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M 



STEAM ENGINES 



A THC 'HOUGH AND PRACTICAL PRESENTATION OF MODERN 
STEAM ENGINE PRACTICE 



BY 

LLEWELLYN V. LUDY, M.E. 

PROFESSOR OF EXPERIMENTAL ENGINEERING, PURDUE UNIVERSITY 
AMERICAN SOCIETY OF MECHANICAL ENGINEERS 



ILLUSTRATED 



AMERICAN TECHNICAL SOCIETY 
CHICAGO 

1917 









COPYRIGHT, 1912, 1917, BY 

AMERICAN TECHNICAL SOCIETY 



COPYRIGHTED IN GREAT BRITAIN 
ALL RIGHTS RESERVED 




FEB 28 1918 

©CI.A4818!Mi 



/>M> / 



INTRODUCTION 

THE modern steam engine, whether it be the majestic Corliss, 
which so silently operates the massive electric generators in 
one of our municipal power plants, or the giant locomotive which 
pulls the Limited at sixty miles an hour, commands our unstinted 
admiration. And yet every movement is so free and perfect in 
its action, every function is performed with such precision and 
regularity, that we lose sight of the wonderful theoretical and 
mechanical development which was necessary to bring these 
machines to their present state of perfection.* 

<I The genius of Watt, the "father" of the steam engine, was so 
great that his basic conception of this, his greatest invention, and 
of many of his minor discoveries in connection with it, remain 
almost as he gave them to the world over a century ago. Yet he 
was so far in advance of the mechanical development of his time 
that his workmen could not build engine cylinders nearer true 
than three-eighths of an inch. Modern builders demand an 
accuracy of at least two-thousandths of an inch — almost two 
hundred times greater. 

<I But mechanical skill is not the only particular in which prog- 
ress had been made. Many minor but important improvements 
have been brought about by a careful study of the theory of heat 
engines. The reduction of enormous heat losses, the use of super- 
heated steam, the idea of compound expansion, the development 
of the Stephenson, Walschaert, and other valve gears — all have 
contributed towards making the steam engine well-nigh mechan- 
ically perfect and as efficient as is inherently possible. 

<I The story has been developed from a historical standpoint and 
along sound theoretical and practical lines. It will be found 
absorbingly interesting and instructive to the stationary engineer 
as well as to all who wish to follow modern steam engineering 
development. The material is particularly adapted to home 
study. If, therefore, the book should prove of real value in 
stimulating the interest of the trained man or the layman in the 
technical developments of the day, the publishers will feel that 
its mission has been accomplished. 



CONTENTS 



PAGE 

Development 1 

Early history 1 

Parts of steam engine 7 

Types and construction 25 

Classification 25 

Simple engines 26 

Compound engines 26 

Stationary engines 31 

Farm or traction engine 50 

Locomotive engines 61 

Water pumps 67 

Special engines 73 

Marine engines 74 

Types of engines 75 

Engine details 81 

Propulsion 88 

Propellers 90 

Management of marine engines 93 

Mechanical and thermal efficiency 105 

Low thermal efficiency inherent 105 

Losses in practical engine 107 

Radiation 108 

Cooling by expansion 109 

Steam condensation and re-evaporation 109 

Exhaust waste 110 

Clearance Ill 

Friction Ill 

Operation economies Ill 

Multiple expansion 112 

Jacketing., 114 

Superheating 1 16 

Condensers 123 

Analysis of engine mechanisms 139 

Crank effort 139 

Flywheel 140 

Governor 146 



CONTENTS 

PAGE 

Erection of steam engines 158 

Operation of steam engines 161 

Engine specifications 169 

Selecting an engine 169 

Drawing up specifications 169 

Contract 174 

Engine costs 175 

Relative cost of operation items 175 

Annual operation expenses 176 

Engine tests 177 

Importance of tests 177 

A. S. M. E. code 177 




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STEAM ENGINES 

PART I 



DEVELOPMENT 



Early History. In the study of this subject, it is thought advis- 
able to review the historical development of the steam engine in 
order that a broad conception of it may be obtained. It is not 
intended, however, to give the history of the steam engine in detail — 
although it is an exceedingly interesting one, which would be bene- 
ficial for any one to review — but rather, a short resume in order 
that the student may be prepared for a detailed study of the mod- 
ern engine. 

The first steam engines of which we have any knowledge were 
described by Hero of Alexandria, in a book written two centuries 
before Christ. Some of them were very ingenious, but the best 
were little more than toys. From the time of Hero until the sev- 
enteenth century little progress was made. At this time, however, 
there was a great need of steam pumps to remove water from the 
coal mines. In 1615, Salomon de Caus devised an arrangement, 
consisting of a vessel having a pipe leading from the bottom which 
was filled with water and then closed. When heat was applied to 
the vessel, steam was formed, which forced the water through the 
discharge pipe. 

Later an engine was constructed in the form of a steam tur- 
bine, but was unsuccessful, and the attention of the inventors was 
again turned to pumps. 

Savery. Finally Thomas Savery completed, in 1693, the first 
commercially successful steam engine. It was very wasteful of 
steam as compared with engines of today but, as being the first 
engine to accomplish its task, it was successful. Savery 's engine, 
Fig. 1, consisted of two oval vessels Ai and A 2 , placed side by side 
and in communication with a boiler B\. The lower parts were con- 



2 STEAM ENGINES 

nected by tubes fitted with suitable valves. In operation, steam 
from the boiler was admitted, say, to the vessel A 2 and the air driven 
out. The steam was then condensed and a vacuum formed by let- 
ting water play over the surface of the vessel. When valve 1 was 
opened, this vacuum drew water from below until the vessel was 
full. The valve was then closed and steam again admitted by 
valve 2, so that on opening valve 3 the water was forced out through 
the delivery pipe C. The two vessels worked alternately. When 
one was filling with water, the other was open to the' boiler and 
was being emptied. Of the two boilers Bi and B 2 , one supplied 
steam to the oval vessels and the other was used for feeding water 





Fig. 1. Early Form of Steam Pumping Engine 



to the first boiler. In operation the second boiler was filled while 
cold, and after a fire had been lighted under it, acted like the vessel 
used by Salomon de Caus and forced a supply of feed water into 
the main boiler. 

A modification of Savery's engine — the pulsometer shown in 
Fig. 2 — is still found in use in places where an ordinary pump could 
not be used and where extreme simplicity is of especial advantage. 
Its valves work automatically and it requires very little attention. 

A serious difficulty with Savery's engine resulted from the fact 
that the height to which water could be raised was limited by the 
pressure which the vessels could sustain. Where the mine was 



STEAM ENGINES 



very deep it was necessary to use several engines, each one raising 
the water a part of the whole distance. The consumption of coal 
in proportion to the work done was about twenty times as great as 
that of a good modern steam engine. This was largely, though not 
entirely, due to the immense amount of steam which was wasted by 
condensation when it came in contact with the water in the oval 
vessels. 

Newcomen. The next great step in the development of the 
steam engine was taken by Newcomen, who in 1705 succeeded in 
developing a scheme which prevented contact between the steam 
and the water to be pumped, thus 
diminishing the amount of steam 
uselessly condensed. He intro- 
duced the first successful engine 
which used a piston working in a 
cylinder. 

In Newcomen's engine, Fig. 3, 
there was a horizontal lever A, 
pivoted at the center, carrying at 
one end a long heavy rod B which 
connected with a pump in the mine 
below. A piston C was hung from 
the other end of the lever and 
worked up and down in a vertical 
cylinder D, which was open at the 
top. Steam acting on the lower 
side of the piston, at atmospheric 
pressure, was admitted from the boiler to the cylinder, and as the 
pressure was the same both above and below the piston, the weight 
of the heavy pump rod raised the piston. A jet of water in the cylin- 
der condensed the steam and formed a vacuum. This left the piston 
with atmospheric pressure above and very little pressure below 
(a partial vacuum), so it was forced down and the pump rod 
raised again. Steam could again be admitted to the cylinder; the 
pump rod would fall ; and the process could be continued indefinitely. 

In the days of Newcomen it was very difficult to obtain good 
workmanship. For this reason it was often necessary to make 
the cylinders of wood. In order to prevent steam from blowing 




Pulsometer 



4 STEAM ENGINES 

around the piston, or air from leaking in where steam was being 
condensed, it was customary to keep a jet of water playing on the 
top of the piston. 

One great trouble with all of these engines was that some one 
was required to open and close the cocks, and boys were generally 
employed to do this work. One boy, in order to get time to play, 
rigged a catch at the end of a cord which was attached to the beam 




Fig. 3. Newcomen's Steam Pumping Engine 



overhead, and this did the work for him. By making the valves in 
this way automatic, made it possible to dispense with the services 
of the boy and at the same time greatly increase the speed of the 
engine. 

The Newcomen engine was improved slightly from time to 
time by different inventors and was very extensively used until the 
time of Watt, a very few of them still being in existence today. 
While this engine was a success and a great improvement over its 



STEAM ENGINES 5 

predecessors, it was still very large, wasteful, and heavy in com- 
parison with the work done, and the cylinders, when made of iron, 
were simply cast and not bored, thus leaving a rough, inner wall. 

Watt. In the year 1763, a small model of a Newcomen engine 
was taken to the shop of an instrument maker in Glasgow, Scot- 
land, to be repaired. This instrument maker, whose name was 
James Watt, had been studying steam engines for some time and 
he became very interested in this model. He was a man of great 
genius, and before he died his inventions had made the steam engine 
so perfect a machine that there has been but one really great improve- 
ment in it since his time, namely, compounding. 

He found that to obtain the best results it was necessary, "first, 
that the temperature of the cylinder should always be the same as 
that of the steam which entered it; and second, that when steam was 
condensed it should be cooled to as low a temperature as possible." 
All improvements in steam-engine efficiency have been in the direc- 
tion of a more complete realization of these two conditions. 

In order to keep the cylinder nearly as hot as the entering 
steam, Watt no longer injected water into the cylinder to condense 
the steam, but used a separate vessel or condenser. He made his 
piston tight by using greater care in construction, so that it was 
unnecessary to have a water seal at the top. He then covered the 
top of the cylinder to prevent air from cooling the piston. 'When 
this was done he could use steam above the piston as well as below; 
this made the engine double acting. 

Also, in the effort to keep the cylinder as hot as the entering 
steam, he enclosed the cylinder in a larger one and filled the space 
between with steam. This was not often done, however, and only 
of late years has the steam jacket been of much advantage. Also, 
the steam was used expansively, that is, the admission of steam was 
stopped when the piston had made a part of its stroke; the rest 
of the stroke was completed by the expansion of the steam already 
admitted. This plan is now used in all engines that are built for 
economy. 

Other inventions made by Watt on his steam engines were: a 
parallel motion, that is, an arrangement of links connecting the end 
of the piston rod with the beam of the engine in such a way as to 
guide the rod almost exactly in a straight line; a throttle valve for 



6 



STEAM ENGINES 



regulating the rate of admission of steam; and a centrifugal governor, 
which controlled the speed of the engine shaft by acting on the 
throttle valve. Watt's engine as finally developed is shown in 
Fig. 4. 

Watt saw that by using high-pressure steam he could get more 
work from it; but as it was not possible to make a very reliable 




Fig. 4. Final Form of Watt's. Steam Pumping Eng 



boiler he never used a pressure of more than seven pounds per square 
inch above the atmosphere. About the year 1800, comparatively 
high pressures came more into use and the non-condensing engine 
was introduced. In Watt's engine, and all those preceding his, a 
vacuum was produced in front of the piston by condensing the steam, 
and either the atmosphere or steam at atmospheric pressure pushed 



STEAM ENGINES 7 

it through the stroke. In the non-condensing engine, using high- 
pressure steam, the space in front of the piston could be opened to 
the atmosphere at exhaust and, although the atmospheric pres- 
sure resisted its motion, the pressure of the steam behind the piston 
was still greater than that of the air. These engines were much 
more simple than the condensing engines, as they required no con- 
denser. 

Compound Pumping Engine. About this time what would 
now be called a compound engine was introduced by Hornblower 
and later by Woolf. It had two cylinders of different size, steam 
being admitted into the smaller one and then passing over into the 
larger. Only a little expansion occurred in the small cylinder and 
much more in the larger one. 

About the year 1814, Woolf introduced a compound pumping 
engine in the mines of Cornwall, but a simpler engine was later intro- 
duced and Woolf's engine fell into disuse. This later engine became 
known as the Cornish pumping engine and was famous for many 
years because of its economy. It was the first engine ever built 
that could compare at all with modern engines in the matter of 
steam consumption. It consisted of a single cylinder placed under 
one end of a beam from the other end of which hung a heavy rod 
which operated a pump at the foot of the shaft. Steam was admitted 
to the upper side of the piston for a short portion of the stroke and 
allowed to expand for the remainder of the stroke. This forced 
the piston down, lifted the heavy pump rod, and filled the pumps 
with water. Then communication was established between the 
upper and under side of the piston, exhaust occurred, and the heavy 
pump rod fell, lifting the piston and forcing the water out of the 
pumps. Steam was cut off at about three-tenths stroke, and the 
pump made about seven or eight complete strokes per minute with a 
short pause at the end of each stroke to allow the valves to close 
easily and the pumps to fill with water. These engines needed great 
care and were in charge of competent men, to whom prizes were fre- 
quently given for the best efficiency, which doubtless accounts for 
their wonderful performance. 

Parts of Steam Engine. Leaving the historical side of the steam 
engine let us now turn to the modern simple steam engine and study 
briefly its construction. Figs. 5, 6, and 7, will serve to illustrate a 



^ 



8 



STEAM ENGINES 



horizontal, center crank engine, all the more important parts being 
numbered. The function of the various parts will be considered in 
detail later in the work. 

Referring to the numbers in Figs. 5, 6, and 7, the names of the 
parts are shown in the following list: 

List of Parts 



Sub-base 1 

Frame 2 

Main bearing caps 3 

Main bearing liners 4 

Cylinder 5 

Cylinder head 6 

False head cover 7 

Valve chest head (head end) 8 

Valve chest head (crank end) 9 

Piston 10 

Piston rings 11 

Piston rod 12 

Piston rod nut (piston end) 13 

Piston rod nut (crosshead end) 14 

Piston rod stuffing box 15 

Piston rod gland 16 

Crosshead 17 

Crosshead shoes 18 

Crosshead adjusting screws 19 

Crosshead pin 20 

Crosshead pin nut 21 

Cross pin washer 22 

Connecting rod 23 

Connecting rod bolts 24 

Connecting rod strap 25 

Crosshead pin box 26 

Crosshead pin box wedge 27 

Adjusting screws 28 

Crank pin box 29 

Crank pin box wedge 30 

Adjusting screws 31 

Crank disks 32 

Crank shaft 33 



Flywheels 34 

Valve pistons 35 

Valve rings 36 

Valve cages 37 

Valve rod 38 

Valve rod nuts (valve end) 39 

Valve rod nuts (ram end) 40 

Valve rod gland 41 

Ram box 42 

Ram box caps 43 

Ram 44 

Ram pin and nut 45 

Ram pin cap 4® 

Eccentric rod connection 1+7 

Eccentric rod 48 

Eccentric rod nut (ram end) 49 

Eccentric rod nut (eccentric end) 50 

Eccentric 51 

Eccentric strap 52 

Dash plate 53 

Dash plate gland 54 

Doors 55 

Door handle 56 

Door clamps 57 

Oil hood 58 

Oil hood handles 59 

Eccentric oil boat 60 

Valve rod oil boat 61 

Oil vent 62 

Sheet steel lagging 63 

Drain cocks 64 

Shaft governor 65 



Sub- Base. The sub-base 1, Fig. 6, is made of a good grade of 
cast iron and is usually heavily ribbed and made high enough to 
permit the wheels to clear the floor. The sub-base is often omitted 
with engines of large size, the engine being set upon a concrete base. 

Frame. The frame 2 is the element or link by which all of the 
parts of the engine are held in place, so that their relative positions 



STEAM ENGINES 



9 



are always maintained to the end that their proper functions may 
be performed. The frame is a heavy, substantial casting so designed 




Fig. 5. Plan View of Modern Simple Engine 



that it is strong enough to take all the stresses put upon it. The 
type, size, and details of the frame vary with the type and size of 




Fig. 6. Side Elevation of Modern Simple Engine 

the engine of which it is a part. Usually the lower guide, valve rod 
guide, and seats for the main bearings are cast integral with it. In 



10 



STEAM ENGINES 



small sizes the cylinder is frequently cast integral with the frame. 
Provision is always made for adjustments necessitated by any wear 
of the frame or parts attached thereto. It is to be noted in Fig. 6, 
that the frame crank case 2 is connected with the crosshead guide. 
It frequently has an opening into the sub-base, thus permitting the 
oil from the crosshead, guides, and crank to drain into a suitable 
receptacle in the sub-base, from which it is taken by means of a drain 
cock conveniently located in the side or end. The crank is enclosed 




f^lr 



Fig. 7. End Elevation and Part Section of Modern Simple Engine 



by a neat, pressed, sheet steel cover, which prevents the oil from 
being thrown outward on the floor while the engine is running. 
Quite frequently the crank cover is made of cast iron. 

Cylinders. The cylinder 5, Fig. 5, is one of the most impor- 
tant parts of the steam engine, for it is in the cylinder that the 
energy of the steam is converted into useful work. The cylinder is 
circular in section and is attached to the bed by means of a number 
of bolts. It is made of close grain, gray cast iron. The casting 
of the cylinder should be done with great care, so as to insure a 
casting free of blow-holes or other defects. 

Fig. 8 illustrates the cylinder in cross section as well as show- 
ing its contained parts. The cylinder barrel 1 is accurately bored 



STEAM ENGINES 



11 



and fitted. Inside of this barrel the piston 2 is driven back and 
forth by the steam, which is admitted alternately on one side and 
then on the other through the ports 18. The piston is connected 
to the crosshead through the piston rod 3. The continuous move- 
ment back and forth of the piston causes the surface of the cylinder 
to wear away, and in order to avoid a shoulder being formed by this 
action, the cylinder is counterbored at each end by an amount 
depending on the size of the cylinder. The diameter of the counter- 



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Fig. 8. Cylinder and Valve Mechanism Shown in Section 



bore 22 is usually about one-quarter of an inch larger than that of 
the cylinder proper, depending, however, somewhat on the size of 
the cylinder. The stroke of the piston is such that the piston moves 
beyond the wearing surface at each stroke, thus preventing any 
shoulder being developed in the cylinder wall. 

The cylinder is attached to the bed of the engine by a number 
of bolts which are placed through the flanges 23 of the cylinder and 
cylinder head. Each end of the cylinder is closed by means of the 
cylinder heads 6 and 9. The cvlinder head 6 is called the back cvlin- 



12 STEAM ENGINES 

der head (head end), and 9 is known as the front cylinder head 
(crank end). In the illustration the front head 9 is a portion of the 
frame, but in many constructions it is entirely independent of the 
frame. In order to have a steam-tight cylinder, it is necessary to 
make a tight joint between the cylinder heads and the cylinder bar- 
rel. This is accomplished by turning both surfaces true, then grind- 
ing the joints with emery and oil. After the joints are well ground 
the heads are tightly drawn up against the cylinder by means of 
bolts suitably arranged. A sheet iron jacket 19 is put around the 
cylinder, leaving an air space 21 between the cylinder walls and the 
jacket. This air space retards the cooling off of the cylinder walls, 
hence initial condensation of the steam in the cylinder is reduced. 
In some types of engines such as locomotives, this air space is filled 
with some non-conducting material such as asbestos. This is also 




Fig. 9. Piston, Showing Piston Rings for Making Steam-Tight Joint3 

sometimes done by builders of stationary engines. It should be 
noted also, that the back cylinder head has an air space for the same 
reason as that given for the space surrounding the cylinder. Since 
condensation does take place in the cylinder, some means must be 
provided for removing the water, hence the drain cocks 64, Fig. 6, 
are placed in the bottom of the cylinder at each end. The pipe 
connection for these cocks enters the cylinder in the counterbore 
near the wearing surface. Any water that may be in the cylinder 
will be forced out through these cocks if they are open. Care must 
be taken that the cylinder is freed of water, for if it is not, on account 
of the incompressibility of water, the cylinder head may be forced 
off or other damage result therefrom. Some cylinders are provided 



STEAM ENGINES 



13 



with relief valves, which automatically open when the pressure from 
any cause reaches a certain amount, thus preventing the bursting 
of a cylinder head. 

Piston Rings. Between the piston 2, Fig. 8, and the walls of 
the cylinder there must be a steam-tight joint, so that the live steam 
can not pass around the piston and be exhausted before expanded, 
otherwise a great waste of power will be incurred. The require- 
ment is fulfilled by having the piston grooved, as shown in Fig. 9, 
and fitted with packing rings. These packing rings, commonly 
called snap rings, are turned up slightly larger in diameter than the 
cylinder and being cut, as shown in Fig. 9, they spring out into the 
cylinder, always pressing against 
the walls and forming an almost 
perfect steam joint. The piston 
of every engine is made with two 
or more of these packing rings. 
The cuts in the rings must not 
be placed directly in line with 
each other, otherwise the steam 
would have a better chance to 
blow through. In order to pre- 
vent this the joints are always 
placed on opposite sides of the 
piston. Packing rings are always 
made of cast iron, and are usu- 
ally turned up to a uniform sec- 
tion. The outside portion and the two sides are carefully machined. 

Pistons. The piston 2, Fig. 8, is usually made of cast iron, 
but sometimes is made of cast steel. It may be a solid disk grooved, 
as in Fig. 9, or the central portion may be cored out, as in Fig. 8. 

Another type of piston that is largely used in marine and some- 
times locomotive service is illustrated in Fig. 10. This is a com- 
paratively light cast steel piston, but at the same time a very strong 
one, due to its conical construction. It will be noted also that only 
the one packing ring 1 is used. This packing ring is much wider 
than the ordinary snap ring and is pressed out against the cylinder 
wall by a number of single leaf springs being placed between the 
body of the piston and packing ring, as shown in Fig. 10 at 2. The 




Part Section Plan and Elevation 
of Conical Piston 



14 STEAM ENGINES 

piston is made with an L-shaped edge 3, a band 4 being bolted on the 
open side of the L, thus forming a groove or opening for the recep- 
tion of the small springs and the packing ring. The connection of 
the piston rod to the piston is also clearly shown. The rod 5 has 
a tapered end which is forced by hydraulic pressure into a tapered 
hole in the piston; the nut 7 is then tightened up and locked by 
placing the plate in position around the nut and fastening it with 
cap screws. This arrangement insures a lasting connection between 
the piston and the piston rod. 

It is essential that the piston be as light as possible in order to 
reduce the amount of work absorbed in pulling it to and fro, and 
also to reduce the wear on the lower portion of the cylinder. 

The piston rod 3, Fig. 9, is fitted into a tapered hole in the pis- 
ton and secured by means of a lock nut and cotter pin placed on the 
back end. Oftentimes the tapered fit is made very tight and the 
piston forced on by hydraulic pressure. An older form of attaching 
the piston rod to the piston is shown in Fig. 8. In this instance the 
rod has a tapered end, which is driven into a tapered hole in the pis- 
ton where it is secured by a nut, no cotter pin being used. The 
other end of the piston rod is threaded, screwed into the crosshead, 
as shown in Fig. 6, and secured by means of a lock nut. In some 
constructions the crosshead end of the piston rod is tapered and 
secured by a key. Many schemes have been employed by different 
manufacturers for fastening the piston rod to the crosshead, all 
of which have their advantages and disadvantages. The piston rod, 
although usually made of a good quality of open hearth steel, is 
frequently made of nickel steel, which possesses great strength. 

Stuffing Box and Packing. As the piston rod passes through the 
front cylinder head, some provision must be made for making a 
steam-tight joint between the piston rod and the cylinder head. This 
is accomplished by means of the stuffing box 4> an d the gland 5, 
shown in Fig. 8. Some form of packing is placed around the piston 
rod within the stuffing box 4 and the gland is forced in by means of 
bolts or a secured cap as shown, thus holding the packing in the box 
and at the same time crowding the packing tightly against the 
piston rod. 

The piston packing may be made of woven strands of hemp or 
cotton; or asbestos may be used. To insure lubrication of the rod 



STEAM ENGINES 



15 



this fibrous packing is soaked in oil before being placed in position. 
In addition to this form of packing there are different compositions 
of rubber, graphite, cotton, etc., also various kinds of metallic pack- 
ing in use. A metallic packing is made of material such as babbitt 
metal, which is a soft alloy of copper, tin, and antimony. This and 
other compositions are used for metallic packing, and the metal, 
being comparatively soft, wears away much more rapidly than 
that of the piston rod. Fig. 11 illustrates one form of packing, 
known as the U. S. Metallic packing. The principle of operation is 
as follows: The babbitt metal rings 2, consisting of three rings cut 
in half, provide the packing and are the only parts which come in 
contact with the rod. These 
rings are forced into the vibrat- 
ing cup 6 against the rod, and 
are fed down as wear takes 
place by the pressure of the 
steam itself. The spring be- 
hind the follower 3 is merely 
intended to hold the rings 
and other parts in place when 
steam is shut off. A ground 
joint is made between the flat 
faces of the vibrating cup 6 and 
the ball joint 4. There is also 
a ground joint between the ball 
joint 4 an d the gland 7. The 
combination of the sliding face of the vibrating cup and the ball joint 
permits the packing to follow the rod freely without any increase in 
friction should it run out of line for any cause. This is an important 
feature, since the wear of the crosshead, guides, piston head, and cyl- 
inder produces an irregular alignment of the piston rod, which would 
injure the packing to a marked degree, if it was not flexible. The 
parts of the packing are held in place by the gland 7, which is bolted 
to the cylinder head. A steam-tight joint is made between the gland 
and the cylinder head by means of a copper gasket. The purpose 
of the swab cup 5 is to hold in place a swab, which is usually made 
of waste, candle wicking, or a braided material, soaked in oil and 
oiled from time to time as a means of keeping the piston rod well 




Fig. 11 



Stuffing Box Packed with Metallic 
Packing 



16 



STEAM ENGINES 



lubricated. In addition to this service, the swab catches and retains 
a considerable amount of dust and grit which would otherwise find 
its way into the cylinder, where it might do harm. It is to be said 

in favor of the various so-called rubber 
packings, that they give very good ser- 
vice. The four different styles of rubber 
packing illustrated in Fig. 12, are not 
composed entirely of rubber, but contain 
other material such as graphite, cotton, 
etc. These different styles of packing 
are used both on piston and valve rods. 
It is to be borne in mind that all which 
has been said with reference to the piston 
rod is equally applicable to valve stem 
packing. The general construction of the 
valve stem glands, vibrating cups, etc., 
is identical with those of the piston rod. 
The same materials are used for the 
packing medium and the same watchful 
care is required in order to obtain satis- 
factory results. Packing is an important 
subject and one which should be care- 
fully looked after. It can not be said 
that any one particular kind or style of 
packing is the proper one to use in every 
case, for a packing which may give very 
satisfactory results under one set of con- 
ditions may utterly fail under another. 
For instance, a packing suitable for low 
steam pressures is not efficient where 
high steam pressures are used, and a 
packing that may give satisfaction with 
high pressures may not in any measure 
meet the requirements imposed upon it by 
the use of superheated steam. Each particular installation is, there- 
fore, a different problem and must be solved in a different manner. 
Valves. In Fig. 8, the valve 11 is shown in position. It will be 
noted that the valve rests upon the valve seat 14 and works between 




Fig. 12. Types of Rubber Packing 



STEAM ENGINES 



17 



the valve seats and the pressure plate 12. The valve 11 is usually 
made of cast iron and may be of many different shapes, as will be 
seen in the study of the various types of engines. There are, how- 
ever, two general types of valves — one, a plain slide or D-valve; 
and the other some form of piston valve. While there are many 
modifications and combinations of these two types, yet they are 
akin to the two types named. The valve in Fig. 8 is of the slide 
valve type. It is what is known as a double ported valve, that is, 
steam is admitted to the cylinder by two edges of the valve by reason 
of the fact that there is an opening through the valve. The pres- 
sure plate 12 is used for the purpose of reducing the area of the valve 
exposed to live steam pressure, it being noted that the portion under 
the hollow space 24 is not in contact with live steam. This reduc- 




Fig. 13. Eccentric Mechanism Showing Rocker and Ram Methods of Connecting 
Eccentric Rod with Valve Rod 



tion of the exposed area is made in order to reduce the amount of 
effort required to pull the valve back and forth. When the surface 
of a valve of medium size is considered and an average steam pres- 
sure per square inch of 180 pounds is being exerted upon it, some 
conception can then be had of the amount of friction that must be 
overcome every time the valve is moved across its seat. To elimi- 
nate a portion of this negative work is the primary object of the 
pressure plate. Pressure plates are of various shapes and designs 
depending of course upon the type of the engine and the valve used. 
One of the advantages the piston valve has over the slide valve 
is that it is almost perfectly balanced by reason of the fact that steam 



18 STEAM ENGINES 

surrounds it on all sides, hence there is no excessive pressure on any 
part of the valve. It is comparatively light and therefore easily 
driven and lubricated. The general form of construction of piston 
valves is illustrated in plan in Figs. 21 and 22. 

Eccentric. The valve is driven by its connection to the shaft 
by means of the valve stem, eccentric rod, and the eccentric. The 
relation of these parts is well illustrated in Fig. 13. The valve shown 
is an ordinary piston valve with flexible snap packing rings 4 similar 
to those previously described for the piston packing rings. In fact, 
the piston valve, as the name implies, behaves very much like the 
steam engine piston. The two piston ends 1 and 2 are held together 
by the valve rod 3. The valve rod has nuts so placed that the pis- 
tons are held the proper distance apart. The valve rods, or stems 
as they are often called, extend beyond the valve box some distance 
and connect with the eccentric rod 5. The manner of making the 
connection between the valve rod and the eccentric rod varies widely, 
this connection being governed largely by the type of engine and 
the exigencies of the case. Fig. 13 shows two methods of making 
this connection, one being accomplished by making use of a rocker 
arm and the other by using a ram. The way in which the rocker 
arm 10 is used, is obvious from the figure. The ram 10 is a square 
block, working in a bearing and so constructed that the valve and 
eccentric rod can be attached to it. When the ram is used, the 
motion is transmitted to the valve in a straight line, hence there is 
less strain upon the connecting parts than if a rocker arm was 
employed. 

The eccentric rod 5, in both cases, is attached at one end to the 
eccentric strap 6 and at the other end to the ram or rocker arm. 
Nuts suitably arranged make the rod secure and at the same time 
provide a means for lengthening or shortening the rod as needs 
demand. The valve and eccentric rod are usually made of mild 
steel turned true and polished. 

The eccentric strap 6 is made of gray cast iron, lined with good 
babbitt metal for a wearing surface upon the eccentric. The strap 
is held on the eccentric by means of the bolts 7. By removing liners 
or shims from between the two sections of the strap, adjustments 
for wear can be made. There are several patented straps on the 
market that possess particular features, but the essential elements 



STEAM ENGINES 19 

of all eccentric straps are about the same. Provision is made for 
lubrication by having an oil cup 11 cast with the strap. 

The eccentric 8 is mounted on the main shaft 9 and is held 
secure in the position desired by means of the set screw 12. Eccen- 
trics for large engines are held by means of one or more set screws 
and a key. For a discussion of the function of the eccentric, the 
student is referred to the instruction book on "Valve Gears." 

Steam Chest. The box 15, Fig. 8, containing the valve and its 
parts, is known as the steam chest. The steam chest cover 16 is 
held in place by studs which pass through the flanges 17 into the 
box. The steam chest is connected to the steam supply by suitable 
pipe connections, 
steam being turned on / m^ 

or off as desired by ™~^ ^ __ - ■-.-—,- M 

means of the throttle ^ wff 

valve. When the ■ itim J^ 

throttle valve is ^^te " ^f 

opened, steam passes wM M K j| 

into the chest through V 'M ML M\ 

the valve, into the §yK W? W^ 

cvlinder, where it is 4^L ^ 



Fig. 14. Typical Crosshead and Pin for Large Size Engine 

expanded and then ejected through the exhaust opening. The 
energy of the steam is transmitted through the piston and piston 
rod to the crosshead 17, Fig. 6, thence to the connecting rod 23, 
crank pin 33, to the main shaft. In order that these parts may 
properly perform the function of transmitting this energy, a correct 
design is highly essential; therefore, a discussion of their construc- 
tion is deemed necessary. 

Crosshead and Connecting Rod. The crosshead is usually made 
of steel which forms a connecting link between the piston rod and 



20 



STEAM ENGINES 



the connecting rod. It is made in various shapes and patterns. 
One type is illustrated in Fig. 6. In engines of larger size, the pre- 
vailing form of the crosshead used is similar to that illustrated in 
Fig. 14. This crosshead consists of a steel casting 1 and two wedges, 
or shoes, 2, which fit over a projection on the outside surface of 1. 
These wedges are either cast or forged and serve as a retainer for 
a layer of babbitt metal on the outside. It will be noted that there 
are oil grooves cut on the surface of 2 in order to facilitate the oil- 
ing of the crosshead guides. These wedges are provided with a 
nut and bolt 4, whereby adjustment for wear can be made as neces- 
sary. Usually there is a slight amount of clearance between the 
crosshead and the guides, but it should not be in any case excessive. 
The piston rod is fitted into the end 3, as already described. The 
connecting rod is attached to the crosshead pin 6, which fits into 
the hole 5 and is held in place by a nut. The crosshead pin 6 is 
made of a good grade of steel and has a portion B which fits into the 



_jol- 




Fig. 15. Solid Forged Steel Connecting Rod 

back side of the crosshead, as viewed, the other portion C fitting 
into the outside part. When the pin is in place, the collar D is 
adjusted and the nut E tightly drawn. The straight portion A 
goes between the sides of the crosshead, and upon it the connecting 
rod brasses bear. 

There are two general types of connecting rods in use, usually 
classified as marine and locomotive. Connecting rods of the marine 
type are as a rule used on engines of comparatively short stroke, 
while those of the locomotive type are employed on engines hav- 
ing a long stroke. 

These rods are forged from open-hearth steel, with solid forged 
ends for the crosshead end, and a square end for the crank end in 
case of the marine type; and a solid forged or forked end for the 
crank end in case of the locomotive type. 

The connecting rod, Fig. 15, is a solid forged steel rod having 
the ends machined out to receive the brasses. The crank end 1 is 



STEAM ENGINES 21 

fitted with a brass or bronze box lined with a good quality of babbitt 
metal. The crosshead end 2 is usually, but not always, fitted in a 
similar manner to that of the crank end. Adjustment for wear is 
made by means of wedges at each end, as shown at 3. These rods 
are usually of rectangular cross section, although round shapes some- 
times are used, especially on small engines. 

The marine type of connecting rod is illustrated in Fig. 16. 
The bod> of the rod is forged similar to the locomotive type, as is 
also the small, or crosshead, end, but the distinguishing difference 
is in the way in which the large, or crank, end is formed. The end 
of the rod is enlarged and finished square, and the box containing 
the crank bearing which is lined with a good wearing material, is 
fastened to the rod proper by means of the bolts. Adjustment for 
wear is made by tightening up the nuts on the bolts. 

It will be seen in Fig. 6 that the connecting rod is the connecting 
link between the crosshead and the crank 33. The length of the 




Fig. 16. Marine Type of Connecting Rod 

connecting rod bears a definite relation to the length of the crank 
radius. The ratio of the length of the connecting rod to that of the 
crank radius varies in practice from four to eight. Occasionally 
conditions demand a greater ratio than eight, but it is seldom less 
than four. 

Fig. 17 illustrates the connection of the piston, crosshead, con- 
necting rod, and crank shaft. The function and construction of the 
piston, crosshead, and connecting rod have been previously dis- 
cussed. However, the figure is valuable in that it shows quite 
clearly the relation of the various parts to each other. The crank 
shaft used on center-crank engines is frequently a solid steel forg- 
ing, which includes the crank pin 2. 

Miscellaneous Parts. In order to compensate for the weight of 
the connecting rod and brasses it is necessary to put counterweights 
on the shaft as shown at 4» Fig. 17. These counterweights are 



22 



STEAM ENGINES 



usually heavy castings, machined to slip over projections on the 
crank shaft, and securely fastened thereto by bolts or set screws. 
The portion of the shaft marked 1, Fig. 17, fits into the bearings 
provided for the main shaft or crank shaft, the length of this bear- 
ing portion being the distance between the counterweights and the 
collars 5. It will be noted that on one end of the shaft is located a 
disk 3. Sometimes this disk is forged as a part of the shaft and at 
other times it is made separate and forced on by hydraulic pressure. 
The purpose of this disk is usually intended to provide a ready 




Fig. 17. Connection of Piston, Crosshead, Connecting Rod, and Crank Shaft 



means of attaching the shaft of an electric generator when a direct 
connected plant is feasible or desired. It may be said here that a 
direct connected plant offers many advantages over a belt-driven 
system. It simplifies the plant, reduces friction, gives greater 
reliability, and makes possible more power in a given space. 

The projection 6 on the other end of the shaft is the axis upon 
which the flywheel is forced and held secure by means of a key. 
The crank pin 2 should be of such ample proportions as to be safe 
against breakage and the heating of the pin or brasses placed upon it. 



STEAM ENGINES 



23 



All engines are not of the center-crank type, but many have a 
side crank, the crank being a disk or a crank arm fastened on the 
end of the main shaft very much in the same manner as the disk 3, 
Fig. 17. In this kind of construction the crank pin is usually a piece 
separate from the crank arm or crank disk, and is connected to it by 
being forced on and then riveted over, or by nuts put on and cot- 
tered. In either the side crank or center crank construction, the 
distance from the center of the axle to the center of the crank pin 
is equal to one-half the stroke of the engine, as for instance, an 
18X24 engine has a crank arm of 12 inches in length, which is just 
one-half of the length of the stroke. In speaking of the size of the 
engine it is customary to mention the diameter of the cylinder first, 
that is, in speaking of an 
18X24 engine is meant a 
cylinder 18 inches in diam- 
eter and a stroke '24 inches. 
The main bearing 4, Fig. 
7, should be designed with 
great care, having liberal 
proportions and lined with 
anti-friction metal, ham- 
mered in place and accu- 
rately bored and scraped 
to fit the shaft. On small 
engines the lower half of the main bearings are usually made 
of a part of the frame, the upper half being a removable cap. 
Between the upper and the lower portion of the bearing, metal 
liners are placed, which afford ready means for making any neces- 
sary adjustments. 

Large engines have a babbitt lined, quarter-boxed main bear- 
ing of ample size, Fig. 18. To provide for both vertical and lateral 
adjustments it consists of four parts carefully machined on all sides 
and scraped to fit accurately. This bearing is so constructed 
that the bottom piece can be removed by slightly raising the shaft. 
The other three parts are removed after taking off the cap. By 
use of the adjusting screws 3, the side 2 and the top 1 may 
be properly adjusted by the sense of feeling when the engine is in 
motion. 




Fig. 18. Section of Babbitt Lined, Quarter- 
Boxed Main Bearing 



24 STEAM ENGINES 

There are many other types of main bearings besides those 
mentioned, but they differ only from those already described in 
some of the minor details. The value of these details varies through 
wide limits, each builder contending for his own particular design. 

A side-crank engine needs but one heavy bearing, such as that 
shown in Fig. 18, as the flywheel end of the shaft, being subjected to 
forces acting in but one direction only, requires a much smaller 
bearing. This outer bearing, Fig. 19, is called an out-board bear- 
ing and is smaller and simpler in construction than the main bear- 
ing. It is supported by a special casting, which has a hollow recess 
into which lubricating oil is poured. The shaft carries one or more 
small chains or rings which fit loosely on the shaft and dip into the 




Fig. 19. Out-Board Bearing of Simpler Construction than Main Bearing 

oil. Thus it is seen that oil is constantly brought in contact with 
the bearing of the shaft. This same scheme of lubrication is also 
used for the main bearing. As the different types of engines are 
considered, the several types of bearings will be noted and discussed. 
The belt wheels 34, Fig. 5, serve a two-fold purpose — one as a 
governing device, the value of which will be discussed later, and the 
other as a means of storing up energy while the piston is in mid- 
stroke, where the crank effort is greater than the resistance to be 
overcome. The belt wheels act as a flywheel and give up this 
energy at the ends of the stroke, thus enabling the engine to run 
over the dead centers. The design of the belt or flywheel is an 
important item in the proper proportioning of a steam engine. Its 
weight and dimensions must be very acurately determined. The 
belt wheel, or flywheel, whichever is employed, is made of cast iron 



STEAM ENGINES 25 

of various sizes, some being cast solid in one piece, others being 
cast in two or more sections. In any case the wheel is forced on 
the shaft and securely fastened thereto by means of a key and set 
screws. 

TYPES AND CONSTRUCTION 

Classification. Thus far an effort has been made to give the 
student some idea of the development of the steam engine and enable 
him to become familiar with the various parts and their functions. 
The natural sequence to the above study is to make a detailed study 
of the several types in use. No hard and fast rule can be given for 
classifying steam engines as they overlap in so many instances. That 
is to say, a simple engine may be either condensing or non-condens- 
ing; it may be high speed or low speed, etc. According to well- 
known authorities, various piston engines may be grouped under the 
following classes: 

r _ T . . ... J Single cylinder 

I. Number of cylmders<, , ,,. . .. , 

J [Multiple cylinder 



II. Construction of cylinders 



[Vertical 
Fixed cylinder \ Horizontal 
[Inclined 



,. . , .. , (Oscillating 

.Movable cylinders _, , 

o- i v [Rotary 

Single acting v 



III. Action of steam 1T . 

Double acting 

[Direct acting 

IV. Transmission of steam power \ [with balance lever or beam 

[indirect actings without balance lever or 

[ beam 

Professor R. H. Thurston in his book entitled "A Manual of 
the Steam Engine" classifies steam engines according to their pur- 
pose and use, as follows: 

T a , .. .„ . /Moderate speed 

I. Stationary mill engines< r 

II. Agriculture engines 

III. Portable and semi-portable engines 

IV. Road locomotives 
V. Railway locomotives 

VI. p„™;™ ™;™/Crank and flywheel 



Pumping enginess^. ' . * 

[Direct acting 

Marine engir 

VIII. Special types 



VII. Marine engines/^ 16 engines 
[Screw engines 



26 STEAM ENGINES 

The same authority further classifies engines according to their 
structure, as follows: 

I. Expansion <„ , 

[Compound 

Direct acting 

Beam 

II. Position of cylinder w , . 
Inverted 

Horizontal 

Inclined 

III. Steam(S° nden t g . 

[Non-condensing 

IV. Pressure/f igh pressure 

[Low pressure 

V. Piston action& cip ( rocatili e 
[Vibrating 

VI. Steam turbines 

VII. Rotary 

T7TTT /Direct connected 

VIII. Connections .- , 
[Geared 

tv n j j.- J Jet condensing 
IX. Condensation^ „ , . 

[Surface condensing 

They are frequently designated by the name of the inventor, designer, 
or constructor, as the Watt, the Corliss, or the Porter engine. 

From the last two groupings it is evident there is no sharp line of 
demarcation, for in many instances engines of one class have essen- 
tial parts similar to those of another type. In this work the classi- 
fication outlined in the last group will be taken as a basis for study. 

Simple Engines. The simplest type of engine is the single 
expansion. It has one cylinder and admits steam for a part of the 
stroke, expands it during the remainder, and exhausts either into 
the atmosphere or into a condenser. Simple engines, Figs. 5 and 6, 
are now used only for comparatively small powers, say 200 h.p. or 
less, and although more extravagant in the use of fuel than the others, 
may still be the most economical financially, if low first cost is an 
important item; if they are not run continuously; or if the load 
fluctuates widely. 

Compound Engines. Compound engines have two cylinders 
known as the high pressure and low pressure, Figs. 20 and 21. It will 
be noted that two different types of compounds are represented, the 
one in Fig. 20 being known as a cross-compound, the two cylinders 



STEAM ENGINES 



27 



being parallel, and the one in Fig. 21, a tandem-compound engine, 
the cylinders being in line with each other. 

Steam enters the smaller or high pressure cylinder, and then 
expands until release, when it is exhausted into the larger cylinder, 
where it expands further. The cylinders should be so proportioned 
that approximately the same amount of work can be done in each, 
which may be accomplished by making the high pressure cylinder 
enough smaller than the low so that when the steam leaves the high 
at a lower pressure than when it entered it, the increased volume of 
the steam may be taken care of and at the same time the increased 
area of the low pressure piston may compensate for the drop in steam 
pressure. 




Fig. 20. Typical Cross-Compound Engine 

Besides being economical, the cross-compound has a distinct 
mechanical advantage. The two cranks may be set at right angles 
so that when one is on dead center, the other is at a position of nearly 
its greatest effort. This makes a dead center impossible, and gives 
a more uniform turning moment. Then the individual parts may be 
made lighter and are thus more easily handled. 

When the cranks of the cross-compound engine are at 90 degrees 
with each other the low pressure piston is not ready to receive the 
steam when the high pressure exhausts; therefore, there must be a 
receiver to hold the steam until admission occurs in the low. Such 
engines are called cross-compound, because steam crosses over from 



28 



STEAM ENGINES 



one side to the other. Sometimes instead of having the cranks at 
90 degrees, they are placed together or opposite. Then the strokes 
begin and end together, and the high can exhaust directly into the 
low without a receiver. 

A tandem-compound engine, Fig. 21, has both pistons on one 
rod, the high pressure piston rod forming the low pressure tail rod. 
Such engines are less expensive because there is but one set of recip- 
rocating parts instead of two, but like simple engines they have the 
disadvantage of dead points. 

Triple Expansion Engines. Triple expansion engines expand 
the steam in three stages instead of two. There are usually three 




Fig. 21. Section of Cylinder and Valves of a Tandem-Compound Engine 

cylinders, viz, the high, the intermediate, and the low, arranged 
with cranks 120 degrees apart. This gives a more uniform turning 
moment than a compound. Sometimes there are four cylinders on 
the triple expansion engine, viz, one high, one intermediate, and 
two low. This arrangement gives better balance and is often used 
in marine work. 

For triple engines there must be a receiver between each two 
cylinders. Fig. 22 shows the essential features of a triple expansion 
engine. 

Quadruple Engines. Quadruple engines expand their steam in 
four stages instead of three. Multiple expansion engines are nearly 
always condensing. 



STEAM ENGINES 



29 



Cylinder Ratios. There are several considerations to be remem- 
bered when proportioning the cylinders of the multiple expansion 
engines. The ratio of the cylinders should be such that each devel- 
ops nearly the same power, and the drop in pressure between the 
cylinders and receivers should be as small as possible. 

There are many formulas in use, some simple, others more com- 
plex involving mathematical calculation. A common rule for com- 
pound engines is to make the ratio of the cylinders equal to the square 
root of the total ratio of expansion. Thus, if the steam has an expan- 




Fig. 22. Section of Essential Features of Triple Expansion Engine 

sion ratio of 9, the ratio of the cylinder volumes will be V 9> or 3 ; that 
is, the low pressure cylinder will have a volume three times as great 
as the high pressure cylinder. If the cylinder ratio is 3 and the 
length of the stroke is the same for both, the diameter of the low 
pressure cylinder will be 1.75 times that of the high pressure cylinder. 

Another rule is to make the cylinder ratio equal to the total 
ratio of expansion multiplied by the fractional part of the stroke com- 
pleted when cut-off occurs in the high pressure cylinder. 

Suppose the ratio of expansion is 9, as above, and that cut-off 
occurs at one-third of the stroke in the high pressure cylinder, the 
ratio of cylinder volumes will be 9Xj, or 3. If cut-off occurs at 
one-half of the stroke, the ratio will be 9Xi, or 4.5. 



30 STEAM ENGINES 

For triple expansion engines the low pressure cylinder is made 
large enough to develop the full power if steam at boiler pressure is 
used. 

The intermediate cylinder is made approximately a mean 
between the high and low. The area of the intermediate piston is 
found by dividing the area of the low by one and one-tenth times the 
square root of the ratio of the low to the high. 

The above may be written thus: 

Area of high pressure _ Area of low pressure cylinder 

cylinder Cut-off of high pressure X ratio of exp. 

. . . . Area of low pressure cylinder 

Area or inter, cyl. = * =^- 

1.1 X V ratio of low to high 

In general, for triple expansion the ratios of the volume of the 
three cylinders are about as follows: 

V x i T 2 : V 3 :: 1:2.25 to 2.75:5 to 8 

For quadruple expansion engines, the ratios are as follows: 

Vi. V 2 : V z i Villi: 2 to 2.33: 4 to 5: 7 to 12 

It is self-evident that the compound engines illustrated are of 
the multiple cylinder class. They also have fixed cylinders and are 
double and direct acting. That is, steam acts on both sides of the 
piston, and the power is delivered directly from the piston to the 
shaft or flywheel without the intervention of a walking beam or 
some other transmitting medium. The engines illustrated in Figs. 
20 and 21, are horizontal, whereas the one shown in Fig. 22 is vertical. 
A horizontal engine is, therefore, an engine whose cylinder is parallel 
to the ground, and a vertical engine is one which has its cylinder or 
cylinders perpendicular to the ground. These engines may also be 
operated either condensing or non-condensing. 

From the foregoing it must be obvious that it is not possible to 
classify an engine within narrow limits, so it appears to be more 
logical to classify them according to the service for which they are 
to be used, as in the second grouping. 

Selection of Type. In the selection and design of an engine 
there are a great many factors to be considered. The engine must 
be as light as possible, and yet must be strong enough to do the work 



STEAM ENGINES 31 

likely to be imposed upon it. The bearings should be large and 
ample in number. Lubrication must be given especial attention if 
high speeds are to be used. Lightness of design tends towards small 
first cost, which is important, but durability and efficiency should 
not be entirely sacrificed for low first cost. In the course of time the 
more expensive engine may prove to be the cheaper as maintenance 
and repairs may amount to considerable on a poorly designed and 
built engine. For some classes of service, however, the cheap engine 
is the one best adapted. For instance, in saw mills, cotton mills, 
and for similar class of service, a low first cost simple engine is the 
one best suited for the work, because the labor employed to operate 
it is often inexperienced and ignorant. In such cases the protection 
and care that can be given the engine is poor, hence the lower the 
value of the property exposed, the less will be the loss resulting from 
the depreciation. On the other hand, if one is selecting an engine 
for a lighting plant in a city, he would more than likely select one of 
the most improved types of high speed, condensing machines. In 
the latter case the first cost would be considerably more than the 
one selected for the saw mill, but the increased efficiency of operation, 
the slight depreciation, and the reduction in maintenance would more 
than compensate for this. 

From the foregoing it is evident that there are many factors to 
be taken into consideration when selecting a steam engine for any 
given service. In the further study of the several different types 
the class of service for which each is best suited will be indicated in 
so far as it is possible to do so. There are, however, some general 
features every engine should possess independent of its class. It 
should be simple in construction, having compactness combined with 
great strength and durability. It should be well balanced and free 
from severe vibration. Accessibility of parts is also an important 
consideration. 

STATIONARY ENGINES 

Simple Side=Crank Type. Stationary engines for ordinary mill 
service, such as machine shops, small power plants, and various 
manufacturing concerns, are generally simple engines operating at 
moderate speed, having either plain slide valves or piston valves. 
There are, however, some cases where compound engines of moder- 



32 STEAM ENGINES 

ate size have been installed in similar plants in more recent years. 
The demand for electric generators has also largely affected the 
design of steam engines for small electric power plants. In speak- 
ing of small plants, in this connection, it may be taken as meaning 
from 25 to 500 horsepower. 

A simple slide valve engine of the side-crank type, which has 
been largely used in plants where a cheap, efficient engine was the 
requirement, is illustrated in Fig. 23. This engine has one slide 
valve, an automatic or shaft governor, and a heavy flywheel which 
is used as a belt pulley. It is built in sizes varying from 9 inches X 
14 inches to 22 inches X 28 inches, and develops a horsepower of 



' A 












- m J$fc "L^gfeaBL 






\ 
i 




I ^Ifl ^|MLJa sir 








iZ^s^^HB 


■fe^^B^W 









Fig. 23. Simple Slide Valve Engine of Side-Crank Type 

/ 

about 45 to 300 according to size of cylinders, steam pressure used, 
and the speed at which the engine is operated. 

Lubrication of the cylinders is secured by the use of a sight feed 
lubrication attached to the steam pipe. The main and crosshead 
bearings are lubricated by oil cups. 

This type of engine has been extensively used in cotton gins 
and saw mills and in small machine shops throughout the country. 
There are, however, several grades on the market, and it may be 
purchased for a comparatively low figure where the work to be done 
does not demand a machine of high grade. This engine has a con- 
crete foundation, is well proportioned, and makes a neat appearance. 



STEAM ENGINES 



33 



Simple Vertical Type. A simple vertical high speed engine that 
is particularly well adapted for isolated lighting plants in factories, 
stores, mines, and aboard ships, is illustrated in cross section in Fig. 
24. It requires little attention, occupies small floor space, and is not 
extravagant in the use of steam. The engine is neatly and well 
designed. It has a large base, which insures stability and rigidity. 
All of the working parts are 
enclosed, but readily acces- 
sible for inspection and re- 
pairs. The frame, cylinders, 
valves, pistons, etc., are 
carefully made and ad- 
justed, and the same gen- 
eral types of these various 
parts conform to the gen- 
eral practice of high speed 
engines. It will be noted 
from the illustration that it 
has a center-crank, auto- 
matic governor, and a pis- 
ton valve. The lubrication 
of the moving parts is ac- 
complished by means of a 
geared pump located in the 
interior of the base of the 
frame. This pump forces 
the oil through pipes and 
grooves to the various bear- 
ings. This type of engine 
is furnished by the makers 
in sizes from 3 J inches X 3 
inches up to 9 inches X 7 inches for general service. Much larger 
vertical engines may be obtained, but are made as a special order. 
The engine illustrated is so designed to operate at speeds from 250 to 
500 revolutions per minute, depending on the size, and uses steam 
pressure from GO to 150 pounds. Its commercial rating is from 1§ 
to 60 horsepower, according to the size of cylinders, steam pressure, 
and speed of operation. 




Fig. 24. Vertical High Speed Engi 



34 STEAM ENGINES 

Advantages of Vertical over Horizontal Type. While the discus- 
sion given above has had to do with a vertical engine of rather small 
dimensions and power, yet it must be borne in mind that vertical 
engines in very large units are built and successfully operated. This 
leads to a discussion of the relative merits of horizontal and vertical 
engines. At the present time the most common type of engine is the 
horizontal direct-acting, that is, an engine whose cylinder is horizon- 
tal and whose piston acts on the crank through a piston rod and a 
connecting rod. In small engines the whole is often on one bed plate. 
Such engines are said to be self-contained. The cylinder is either 
bolted to the back of the bed plate or rests directly on it. 

In marine work vertical engines are used in almost every case, on 
account of the saving of floor space, which is so important in a vessel. 
This saving of space is also a very important factor in many other cases, 
such as in crowded engine rooms in cities where land is expensive. 

A second advantage of the vertical over the horizontal engine is 
the reduction of the cylinder friction and unequal wear in the cylinder 
of the latter. In the horizontal engine the piston is generally sup- 
ported by resting on the cylinder, which is gradually worn until it is 
no longer round, causing leakage of steam from one side to the other. 
This is entirely avoided in the vertical engine. 

Still another advantage of the vertical engine is the greater ease 
of balancing the moving parts so that there shall be no jarring or shak- 
ing. It is impossible to perfectly balance a steam engine of one or 
two cylinders. If it is balanced so there is no tendency to shake side- 
wise it will shake endwise; and if it is balanced endwise it will shake 
sidewise. The jarring is due to the back and forth motion of the 
reciprocating parts and the centrifugal force of the crank and the 
connecting rod. The crank can be readily balanced by making it 
exte-nd as far on one side of the shaft as it does on the other, but the 
piston and the connecting rod are more difficult to balance. The 
effect of jarring can be greatly reduced, if the crank be balanced and 
the endwise throw made to come in line with the foundation, which 
should be heavy enough to absorb the vibration transmitted. In a 
horizontal engine this endwise throw not being in line with the 
foundation will cause vibration in the engine itself. 

In machines that can be anchored down to a massive foundation, 
a state of defective balance only results in straining the parts and 



STEAM ENGINES 



35 



causing needless wear and friction at the crank-shaft bearings and 
elsewhere, and in communicating some tremor to the ground. The 
problem of balancing is much more of consequence in locomotive and 
marine engines. 

To sum up the general advantages of the vertical engines : they 




Fig. 25. Buckeye Vertical Cross-Compound Engine 

have less cylinder wear, they take up less floor space, and they can 
be better balanced. In addition to these there are certain advantages 
which vertical engines have for certain kinds of work. 

Disadvantages of Vertical Type. The pressure on the crank pin 
is greater during the down stroke than during the up stroke, because 



36 



STEAM ENGINES 



during the down stroke the weight of the reciprocating parts is added 
to the steam pressure, and during the up stroke this weight is sub- 
tracted. 

Another difficulty is that in large engines the various parts are 
on such different levels that they require considerable climbing. 
This requires more attendants and is -sometimes the cause for neglect 
of the engine. The foundations for vertical engines need to be deeper 
than those for horizontal engines, yet they do not need to be as broad. 

Buckeye Vertical Cross=Compound Type. The development of 
electrical machinery and the increased demand for power in con- 





& 

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\ l:Li 


H QypPitir 


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hhSw 



Fig. 26. Simple Corlisa Engine, Showing Valve Mechanism 

gested city locations, where land is very expensive and buildings costly 
because of their great height, has been the primary cause of the devel- 
opment of large vertical steam engines of various types. The engine, 
Fig. 25, represents a vertical cross-compound engine as built by the 
Buckeye Engine Company, which is especially well adapted to elec- 
tric railway and power and lighting plants, when floor space is limited. 
The engine may be obtained either as a side or a center crank design. 
This engine and simple horizontal engines of the same make are typical 
representatives of economical, high speed engines. They are high 
priced, but the economy of operation and maintenance make them 



STEAM ENGINES 37 

very desirable. The vertical engine illustrated may be obtained in 
sizes developing from 75 to 3,000 horsepower. A discussion of the 
valve gear used on Buckeye engines is to be found in the instruction 
paper on "Valve Gears." It is a double valve, giving automatic 
cut-off as distinguished from throttling cut-off regulation. 

Corliss Type. A general utility engine of the highest type both 
from the standpoint of design and economy of operation and main- 
tenance is the Corliss engine. It is to be found in electric railway 
power stations ; in large and small pumping stations ; in blast furnaces 
and rolling mills; in textile and flour mills; in machine shops and office 
buildings ; in technical schools and colleges ; and in nearly all kinds of 
industrial plants in this country and abroad. The Corliss engine is 
built in various types, styles, and patterns of any designed capacity 
up to 10,000 horsepower. 

Fig. 26 shows the valve connection and manner of operation of 
a simple Corliss engine. It will be noted that the engine is governed 
by a fly-ball governor which is driven by a belt connection to the main 
shaft. This governor is connected to the steam valves by reach rods. 
The speed is automatically governed by variation of the point of cut- 
off. This engine, as well as most engines of this type, has large well- 
proportioned frames, cylinders, etc. Good workmanship and mate- 
rial enter into its construction, hence it is known as a high- 
priced engine; but, on the other hand, it is perhaps the most econom- 
ical in the use of steam. 

Valve Mechanism. The distinguishing feature of the Corliss 
engine is its valve mechanism, a good view of which may be seen in 
Fig. 27. The gear has four valves, the two top ones being the admis- 
sion or steam valves and the two lower ones the exhaust valves. 
There is a connecting rod 7, Fig. 27, which is connected to the eccen- 
tric through a rocker arm, and another rod, as may be seen in Fig. 2G. 
As the shaft revolves, the rod 7, due to its connection to the eccentric, 
moves back and forth, and, by reason of its connection through the 
clamp 8 to the wrist plate 6, the latter is made to oscillate. The 
wrist plate 6 is attached to the frame by a pivot projection. The rods 
9 have a right and left screw adjustment on each end and transmit 
motion from the pins 1 4 on the wrist plate 6 to the steam and exhaust 
valve bell cranks 10 and 15, respectively. These valves receive 
motion in such a manner as to open and close the ports rapidl". 



38 



STEAM ENGINES 



The steam valve bell crank 10 is free to rotate on projections of the 
bonnet and carries at the end of the lever shown nearly horizontal 
the brass hook 3 which engages with the catch block. This catch 
block is rigidly attached to the valve lever 13, which is keyed to the 
end of the valve stem, the latter transmitting motion to the valve. 
Attached to the valve lever 13 is the dashpot piston rod 4- The hook 
is so made that it may be automatically tripped when the back part 
of the hook comes in contact with a cam which is operated by the 




Fig. 27. Corliss Valve Mechanism in Detail 



arm 2 connected to the governor by the reach rod 1. The operation 
of the mechanism is such that the hook may be disengaged at any 
point of its travel by means of the cam coming in contact with the 
tripping leg of the hook 3 and causing it to rotate on the pin and 
move the steel catch out of engagement with the catch block. 

The slowing down of the engine, in consequence of reduced steam 
pressure or an increased load, causes the catch to hold its contact 
longer and the steam to be admitted longer. In the event that the 



STEAM ENGINES 



39 




speed be increased in consequence of increased steam pressure or 
diminished load, the hook would be tripped by the cam and the admis- 
sion valve would be quickly closed by the vacuum dashpot 5. It 
must be evident from the foregoing that the regulation obtained by this 
device must be very sensitive to any change of speed or load. The 
dashpot 5 closes the steam valve when the hook is tripped by the cam. 

The cylinders have four cylindrical holes accurately bored at 
the four corners, as is shown at 11 and 12 in Fig. 27. Into these open- 
ings the valves are placed with their stems and proper packing devices. 
The seats of the valves are circular. The portion of the valve marked 
2 and 1, Fig. 28, is circular, whereas the remaining portion may have 
any shape, depending upon the requirements of the design. The 
valve stem 5-4-0 is also irreg- 
ular in shape. The portion 4 
fits into the slot 3 of the valve 
and round portions 5 and 6 
serve as bearings and as means 
for attaching the driving 
mechanism. 

Advantages and Disadvan- 
tages of Corliss Type. Per- 
haps one of the chief disad- 
vantages of the Corliss engine is the large amount of floor space 
required, a factor which often precludes its use. It possesses 
many advantages, however, chief among which may be men- 
tioned the rapid and wide opening of the steam and exhaust ports; 
shortness and directness of ports, which results in small clearance; 
the adaptation of the steam valve to the functions of cut-off valves; 
and the location of the exhaust ports at the bottom side of the cylin- 
der, thus draining the cylinders perfectly. Each of these various 
factors contribute to good engine performance, and their combina- 
tion has resulted in making the Corliss engine one of the most eco- 
nomical engines manufactured. It will operate upon from sixteen to 
eighteen pounds of steam per indicated horsepower per hour. 

Angle=Compound Type. As an outgrowth of the demand for 
an engine of high speed and one that will occupy a small space, but 
which, at the same time, will be economical in the use of steam, there 
has been developed the angle-compound engine shown in Fig. 29. 




Fig. 28. Corliss Valve and Valve Stem 



40 



STEAM ENGINES 



Balancing. In an ordinary high speed steam engine, the inertia 
of the reciprocating parts — namely, the crosshead, piston, and 
piston rod — and the crosshead end of the connecting rod, is con- 
siderable. If a steam engine is to be installed in office buildings, 
apartment houses, or in other houses where freedom from vibration 
is a prime requisite, it becomes 
almost a necessity for the engine to 
be perfectly balanced. On an ordi- 
nary reciprocating engine it is 
almost impossible to obtain perfect 
balancing for two reasons: 

First, because of the angularity 
of the connecting rod, which causes 
the rate of acceleration of the recip- 
rocating parts to be much faster 
at one end than the other, therefore, 
the counterweight which exactly 




Fig. 29. Section of Angle-Compound Engine 



balances the forces at one end would be either too light or too 
heavy at the other end. 

Second, the counterweight at all positions in the revolution of 
the shaft exerts a radial force and when the counterweight is above 
or below the center of the shaft, there are no reciprocating parts 
developing a counteracting force, hence the centrifugal force of the 



STEAM ENGINES 41 

counterweight exerts a powerful unbalanced vertical force. (This 
has been observed a number of times in locomotive practice where 
the rails have been bent by the extremely heavy blows of the unbal- 
anced forces.) 

In tests at Purdue University on their locomotive testing plant, 
it was clearly demonstrated that the unbalanced vertical forces are 
so great at high speeds that the locomotive driver is at times lifted 
clear off the track. It is obvious from the foregoing that the ques- 
tion of balancing is a serious one, and one that should be carefully 
considered. A thorough study of the question would involve con- 
siderable time and space and the use of higher mathematics. 

The several engine builders who put the angle-compound engine 
upon the market claim for it an elimination of the balancing difficulty. 
As will be seen from the illustration, the angle-compound consists 
in combining two engines in such a manner that one crank pin serves 
both. The high pressure and the low pressure cylinders are placed 
at 90 degrees from each other in the plane of rotation of the crank. 
The horizontal engine is arranged so that it is perfectly balanced 
along its horizontal axis, but is, of course, badly out of balance ver- 
tically. On the other hand, the vertical engine is perfectly balanced 
along its vertical axis, but is out of balance in a horizontal direction. 
The above statements are true only when we consider each engine 
separately. When the engines are placed together, the unbalanced 
effect on one tends to neutralize that of the other. Their relation 
is such that the same counterbalance serves for both engines. It is 
claimed for this arrangement that there are four points in the revo- 
lution where a perfect balance exists and the resultant effect is to 
give almost a perfect balance. Another point of interest with these 
engines is that there are no dead centers; hence by employing a 
by-pass connecting the two cylinders, the engine can be easily started 
from any position of the crank. 

Summary of Advantages. This type of engine, therefore, pos- 
sesses the advantage of good balancing; it occupies about one-half 
of the floor space of a simple engine of the same power; and the 
compounding reduces its steam consumption considerably below 
that of a plain slide valve engine. 

Uniflow Steam Engine. A type of engine which has a very 
extensive use in Europe, and which is just beginning to be manu- 



42 



STEAM ENGINES 



factured in this country is the Uniflow engine. Mr. L. J. Todd, in 
1886, took out patents in England covering the principle of the 
Uniflow engine, but Professor Stumpf of Charlottenburg, Germany, 
deserves credit for developing the engine and for making it a prac- 
tical success. In Europe the high cost of fuel makes even small 
economies in the use of steam of considerable value. The Uniflow 
engine was designed to secure better economy in the use of steam 
than is possible with other steam engines of equal power. As used 
in Europe, the poppet type of valve is almost universally employed, 
because of the better results it gives with superheated steam, 
which is used practically to the exclusion of saturated steam. The 




Fig. 30. Sectional View of Uniflow Engine 
Courtesy of Nordberg Manufacturing Company, Milwaukee, Wisconsin 

Uniflow engine is now manufactured in the United States by a few 
concerns, the Nordberg Company being one of the first to develop 
and build a successful engine of this type in this country. 

Method of Action of Nordberg Engine. A cross-section view of 
the Uniflow engine as manufactured by the Nordberg Manufacturing 
Company is shown in Fig. 30. Steam comes to the engine through 
the inlet S and is led through the passages shown to either admission 
valve A. These valves are of the Corliss type, not only to conform 
with American practice,. but because, with saturated steam, they give 
as good results as the poppet type and are less expensive to construct. 
The steam is exhausted through a ring of ports cast in the middle of 
the cylinder and is conducted away by the exhaust pipe shown below. 



STEAM ENGINES 



43 



Boiler Pressure 




Fig. 31. 



/Tbso/i/te Vacuum 
Indicator card for Uniflow Engine 
Operating Condensing 



Thus it is seen that the piston performs the duty of an exhaust valve 
by uncovering and covering these exhaust ports. J) is a relief valve 
of large size, communicating with chamber B, which is separated by a 
bridge wall in the cylinder 
head from the live steam 
space above. This relief valve 
serves two purposes : first, it 
relieves the cylinder of any 
water that may get into it; 
and second, it opens auto- 
matically in case the vacuum 
is lost and prevents the engine 
from compressing above line 
pressure. Also, if it is desired 
to run the engine non-condens- 
ing instead of condensing, the 
relief valve D may be backed 
off of its seat, thus giving the 
chambers BB as the additional clearance volume which is required for 
non-condensing operation. The drums CC on each side of S relieve 
the cylinder and cylinder heads from the strains caused by the 
expansion of the inlet pipe. 



Boiler Pressure 




Absolute Vacuum 



Fig. 32. Indicator Card for Uniflow Engine 
Operating Non-Condensing 



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Fig. 33. 



50 75 /OO /?5 150 /75 ?00 ?£J 
Percentage of l/nit Load 

Economy Curve for Uniflow Engine 
Operating Condensing 







































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£5 50 75 100 1^5 /50 175 FOO ^^5 

Percentage of l/nit L oad 

Fig. 34. Economy Curve for Uniflow Engine 
Operating Non-Condensing 



Typical Indicator Cards. Typical indicator cards for a Uniflow 
engine with condensing and non-condensing operation are shown in 
Figs. 31 and 32, respectively. Figs. 33 and 34 show economy curves 
when operating, condensing and non-condensing. The cards show 
the effect of the large exhaust area by the rapid falling off of the pres- 
sure as soon as the piston has uncovered the exhaust ports and also 
the gradual and high compression which is obtained. The economy 



44 



STEAM ENGINES 



curves show that an overload of 100 per cent requires only 10 per cent 
more steam than for full-load operation when the engine runs con- 
densing, and but 12 per cent more when operating non-condensing. 
Chief Factor in High Economy. The chief factor in the high 
economy of the Uniflow engine is the great reduction of initial con- 
densation. In the ordinary steam engine the piston head and the 
cylinder head in particular are exposed to the low temperature of 
the exhaust steam, which cools them considerably and leaves them 
cooler than the incoming steam. This causes the great loss known 
as initial condensation. In the Uniflow engine the exhaust steam does 
not pass out near the head of the cylinder, and so does not leave the 




Fig. 35. Cylinder and Valve Arrangement in Skinner Unaflow Engine. 

Piston on Head-End Dead Center and Exhaust Taking 

Place Through Central Ports 

cylinder and piston heads cool; and in addition, the compression is 
carried to line pressure, so that when a fresh supply of steam enters 
the cylinder it meets surfaces of practically the same temperature as 
its own. Furthermore, the walls of the cylinder in the Uniflow 
engine are exposed at each successive point in the stroke to tem- 
peratures which are more nearly the same than they are in the usual 
counter-flow engine; this also helps the engine economy. 

Cylinder and Valve Arrangement in Skinner Engine. The form of 
cylinder and valve arrangement used in the Unaflow engine, built 
by the Skinner Engine Company, Erie, Pennsylvania, is illustrated 
in Figs. 35 and 36. It will be noticed that the steam valves 



STEAM ENGINES 



45 



are of the poppet type and are located on the top of the cylinder. 
Exhaust takes place through central ports in the usual way and also 
through the auxiliary exhaust valves shown on the bottom side. 
Fig. 35 shows the piston on head-end dead center with the steam 
valve at admission and exhaust taking place through the central 
ports. Fig. 36 shows the central exhaust ports closed, the steam 
valve on the head end closed, and exhaust taking place through the 
auxiliary exhaust valve on the crank end. 

When the engine is operating non-condensing, the auxiliary 
exhaust valve for the end in question is opened by the valve-gear 
mechanism at the point when the central exhaust ports are just 




Fig. 36. Section of Unaflow Engine Showing Central Exhaust Ports 

Closed and Exhaust Taking Place Through Auxiliary 

Exhaust Valve on Crank End 



closing, and compression commences at about 35 per cent of the 
stroke. When operating condensing, the valve-gear mechanism 
controlling the auxiliary exhaust is automatically disengaged when 
the vacuum reaches a predetermined amount. Under these con- 
ditions the auxiliary exhaust valves remain closed and compression 
begins at about 90 per cent of the stroke. The construction is such 
that if when operating condensing the vacuum should fail, the aux- 
iliary exhaust valves are automatically thrown into operation. 

American Locomobile. The locomobile is already highly 
developed in Europe, particularly in Germany, but in this country 
developments have just recently begun. On account of its high 



46 STEAM ENGINES 

efficiency, a description of its construction and operation seems 
desirable. 

This apparatus is really a complete power plant all contained 
in a single unit. It consists of a steam boiler with furnace, super- 
heater, and reheater; a compound steam engine with condenser and 
vacuum pump; a feed-water heater; and a boiler feed pump. It is 
now being constructed by different American manufacturers, but that 
built by the Buckeye Engine Company will be taken as typical, since 
they were the first builders of locomobiles in the United States. 

Details of Bower Plant. Referring to Fig. 37, the path of the 
gases and steam can be traced through the plant, and some of the 
mechanical features can be seen. Consider first the boiler, furnace, 
superheater, and reheater. The former is an internally fired, fire- 
tube boiler, the combustion chamber being at A and the fire tubes 
at B. Beyond these tubes is the circular pipe coil C, which is the 
superheater, and still further on is the reheater D, consisting of loops 
of pipe expanded into two headers, as shown. The furnace gases from 
A pass directly through B, C, and D, and then out to the stack 
through the connection shown in the floor. The boiler is supported 
on cradle blocks X, and the superheater and reheater piping is hung 
from horizontal beams, as shown. 

The steam is led from the dome E to the rear end of the super- 
heater and leaves it at the front end, going straight up to the high- 
pressure cylinder of the engine. Leaving the high-pressure cylinder, 
the steam is carried to the front end of the reheater and, leaving at 
the opposite end, is conducted to the low-pressure cylinder of the 
engine. From the low-pressure cylinder the steam is conducted to a 
feed-water heater and then to the condenser, neither of which are 
shown in the figure. In both superheater and reheater, the steam is 
made to flow against the direction of flow of the furnace gases so 
that the steam will enter the engine cylinder at a higher temperature. 

The engine, as can be seen, is mounted directly on the boiler. 
The saddle F, bolted to the boiler shell, supports the engine bed, which 
is securely fastened to it. The engine frame is permitted to slide on 
the saddle G so as to allow for unequal expansion between the boiler 
shell and the engine frame. At the head end of the low-pressure 
cylinder the yoke Y Y supports the cylinder casting. 

Fig. 38 shows the relative temperatures of the steam and the 



STEAM ENGINES 



47 




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o a 



c 23 




Ph o 



2 S 



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go s 



S =? 



STEAM ENGINES 



49 



gas at various points in their respective paths. The figure is self- 
explanatory, except that the feed-water heater, condenser, and 
vacuum pump shown in the upper right-hand corner are put there 
merely for convenience of illustration. In the actual locomobile 
they are situated alongside the boiler in some convenient manner. 
The temperatures here shown are approximate and would vary, of 
course, with different coals, combustion rates, steam pressures, etc. 
Fig. 38 also clearly shows the manner in which the waste gases 
circulate around the high- and low-pressure cylinders. 



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Indicated Horsepower 



Fig. 39. Graphical Results of Locomobile Economy Tests 



The big saving aimed at in the locomobile is the reduction of 
radiation and condensation losses to a minimum. This would mean 
of course that a greater amount of work could be generated in the 
engine by the burning of the same amount of coal. In tests con- 
ducted in this country, the locomobile has generated an indicated 
horsepower on less than two pounds of coal, and has used approx- 
imately ten pounds of water. Fig. 39 shows graphically the results 
of tests, which are remarkable considering the size of the unit. 

General Survey of Stationary Types. The treatment of the 
subject of mill or stationary engines, in so far as the scope of this 



50 STEAM ENGINES 

work will permit, has been covered by the discussions given concern- 
ing the plain slide valve engine, the vertical engine of small units, 
the vertical engines for large installations, the compound and tan- 
dem engines which are being used more and more, and finally by a 
consideration of the most economical engine of all, the Corliss, whether 
operated simple or compound. In addition to the types mentioned 
there are a large number of other makes, which have distinguishing 
features and which give good service, but yet the principles enumer- 
ated in the types already discussed fulfill all the requirements likely 
to be made upon stationary plants. Hence a discussion of other 
makes is not thought necessary. 

FARM OR TRACTION ENGINE 

The advancement of scientific and progressive farming has made 
the farm engine of more interest and importance than ever before; 
in fact, the demands of the active farmers in recent years have taxed 
the builders of such equipment to the limit of their output. The 
steam engine is used for a large variety of purposes upon the mod- 
ern large farm, and appears most commonly in the form of the so-called 
traction engine. It is used for plowing, digging ditches, building of 
roadways, logging purposes, running threshers, and numerous other 
purposes. Various types of stationary engines of small power are 
also to be found in use on the farm, the small gas engines now hav- 
ing been perfected to such a degree that they are rapidly replacing 
the steam engine. 

General Description. The traction engine is really more than 
simply an engine; in fact, it is a self-contained power plant. It con- 
sists of a simple or compound engine, a boiler for supplying the steam 
required by the engine, and the transmission mechanism, together 
with all the auxiliaries necessary for a complete power plant. A good 
type of a general utility traction engine is shown in Fig. 40. It con- 
sists of a boiler of the locomotive type, carried by four wheels, the 
two front ones serving as a means for guiding, and the two rear 
being the ones which receive the power and known as the driving 
wheels. In order to prevent the slipping of the rear wheels when 
doing heavy hauling, they are made with heavy projecting lugs or 
cleats which are forced into the ground by the weight of the machine. 
The engine, which is mounted on the side of the boiler, as may be 



STEAM ENGINES 



51 




52 STEAM ENGINES 

seen in the illustration, is a plain slide valve engine of the side-crank 
type. The speed is regulated by an ordinary fly-ball, centrifugal 
governor. The construction of the various parts of the engine are 
similar to those previously described in this work. The same 
watchful care should be given to the lubrication, operation, and 
maintenance of this engine as to any other, when economy, durability, 
and reliability are desired. It should be noted that both cross-com- 
pound and tandem-compound engines are used as well as simple 
engines in this class of service, and that various types of valves find 
application. 

In order to make clear the construction and operation of the 
traction engine, a view showing the rear wheels, platform, and side 
tanks removed is shown in Fig. 41. The means provided for guid- 
ing, reversing, and driving this engine is clearly illustrated. It is 
evident that the type of boiler used is similar to that of the locomo- 
tive boiler, having a narrow fire box. It has an extended front end 1 
and stack 2 for carrying away the gases of combustion. The boiler 
is mounted upon the front wheels through the pivoted pedestal con- 
nection 3. It is supported on the rear wheels, by having the rear 
axle extend beneath the fire box, or by having the supporting ele- 
ments riveted to the side sheets as in Fig. 41. 

Operation of Plant. Reversing Mechanism. The operation of 
the plant is about as follows : If the engineer desires to go forward 
the mechanism is placed in forward gear by means of the reversing 
lever 29, the reversing being accomplished by means of a swinging 
eccentric, which can be thrown across the shaft at the discretion of 
the operator. (On some types of traction engines, a reversing link 
mechanism is used.) 

Transmission. Having adjusted the reversing gear in accord 
with the desired direction, the throttle valve of the engine is opened by 
moving the lever 30. The opening of the throttle valve starts the 
the engine shaft 12, which carries the flywheel 11. On the engine 
shaft behind the flywheel is keyed a small spur gear which is in mesh 
with the larger gear 13, which in turn meshes with the gear 14- As 
the engine shaft revolves, the small gear in the shaft revolves, which 
transmits its motion to 13 and on to the small gear 15, which is 
keyed to the shaft driven by the wheel 14. The gear wheel IS, Figs. 
40 and 41, is in mesh with an annular gear on the drive wheel U Fig. 



STEAM ENGINES 



53 




54 



STEAM ENGINES 



40; hence, by reason of this connection, the large wheel is made to 
revolve. The shaft carrying gear wheel 15 extends beneath the 
boiler to the opposite side and drives a set of gear wheels which causes 
the other driving wheel to revolve with the one just considered. 

Running Gear. The axle 16 of the wheel has a sliding head 17 
attached to it. This head is free to move up and down in guides 
securely fastened to the fire box. This sliding head works against 
a spring, which is contained in the box 18. This spring reduces the 
shocks to which the machine is subjected when on the road, hence, 

the engine is much easier to 
ride than it otherwise would 
be. In addition to the easy 
riding qualities, it also re- 
lieves the parts of the ma- 
chine of stresses and strains 
due to sudden jolts, which 
would be detrimental to the 
durability of the machine as 
a whole. 

Steering Gear. The engine 
is guided by the hand wheel 
10. It will be noted that a 
chain is connected to the 
front axle on either side of 
the pivotal point. This 
chain wraps around a cam 
arrangement on the shaft 
which carries the small gear wheel 8. The wheel 8 is in mesh with 
the worm 9, which may be turned by the hand wheel 10. If the 
driver when moving forward should wish to turn to the right, for 
instance, he would turn the hand wheel so the wheel 8 would be 
driven counter-clockwise, and in so doing the chain 6 would be 
shortened, the chain 7 lengthened, the wheel 5 would be cut in, and 
the machine would turn to the right. If it was desired to go in the 
opposite direction, the reverse operation would be carried out, that is, 
gear 8 would be revolved clockwise. 

It is sometimes difficult to operate the steering gear by hand, 
especially in large traction engines and in places where a heavy load 




Fig. 42. 



Friction Gear Device for Steering 
Traction Engine 



STEAM ENGINES 55 

is being driven over rough ground ; hence, some engines are provided 
with a friction gear device. This attachment, Fig. 42, is exceedingly 
simple, and when it is used the engine furnishes power to guide itself. 
It consists of a shaft 2 extending from the worm gear 1 to a bracket 
on the side of the boiler in front of the main shaft. On top of this 
vertical shaft is a horizontal miter gear 3 arranged to engage alter- 
nately with two vertical gears, one at the right 5 and the other at the 
left Jf.. These vertical gears are on a shaft run by a chain of small 
gearing 6 from the engine shaft. They are thrown in or out, at the 
pleasure of the operator, by means of a shifting yoke which is worked 
by a straight rod extending back to the right-hand side of the engi- 
neer. A lever at the end of this rod is within easy reach all the time. 
By moving it forward or backward, the engine is guided to the right 
or left, as desired. If the lever remains at the center, the engine guides 
straight. An extension rod is placed on the rear end connecting with 
a hand lever' at the left side of the platform, so that the engine may 
be guided equally well from either side. To operate this steering 
lever requires no appreciable exertion on the part of the engineer. 

Friction Clutch. A friction clutch is provided in the flywheel, 
which permits the engine to be operated without driving the machine 
forward on the road. With the engine running at full speed, the 
clutch can be gradually thrown into action, and the machine will 
start forward on the road without any sudden shocks. The clutch 
is operated by the lever 31, Fig. 41. By disconnecting the engine 
from the flywheel, a high speed can be obtained, so that by throw- 
ing the clutch in gear quickly the engine is often able to pull the 
machine out of difficult places. Oftentimes it is desired to oper- 
ate the engine independently of the traction wheels for the purpose 
of running the thresher, saw mill, electric generator, or for other pur- 
poses, hence some form of clutch is necessary. 

Brake. A friction brake is operated by a system of levers and 
rods as 19, 20, and 21, Fig. 41. The operator can apply the brake 
by pushing downward upon the foot piece on the lever 19. The 
amount of air admitted to the fire box is controlled by the two dam- 
pers 22 and 26, which may be manipulated by the levers 24 and 27. 

Water Tanks. In Fig. 40, large tanks 2, 3, and 4, are shown. 
These tanks are water reservoirs from which the supply pumps take 
water and deliver it to the boiler. Opposite the tank 2 is a bin for 



56 STEAM ENGINES 

holding the fuel, which may be wood, coal, or straw, depending upon 
the location and character of work to be done. If the traction engine 
is used for threshing purposes, it would have a fire box arranged for 
burning straw; whereas if it was being used in a logging camp or a 
saw mill, the available fuel would be wood, hence the fire box would 
be constructed accordingly. 

Boiler. Since it is necessary to have a high-grade, durable, and 
economical boiler in order to have an efficient and reliable machine, 
it is thought advisable to call especial attention to the type of boil- 
ers used in this connection and point out some of their good and bad 
features. It was mentioned in the description of the traction engine, 
Fig. 40, that a locomotive type of boiler with some modifications was 
used. Fig. 43 illustrates such a boiler. It is of the fire tube horizon- 




Fig. 43. Traction Boiler of the Locomotive Type 

tal type. The fire box 1 is of a horizontal rectangular construction 
with open grate bars 2 and ash pit 3, below. The fuel, either wood 
or coal, is fed through the fire door 5, and the ash is removed through 
the door 4- The products of combustion, such as smoke, hot gases, 
etc., pass through the tubes 10 into the front end 12, from whence 
they are exhausted through the opening 13 and the smoke stack into 
the atmosphere. If straw is to be used as fuel, a brick arch is placed 
in the fire box which deflects the gases toward the fire door so that, 
after passing over the arch, they are drawn out through the tubes 
in the usual manner. It is also necessary to put in different grate 
bars where straw is used, as the bars must be closer together so the 
fuel will not drop through into the ash pan. 



STEAM ENGINES 57 

It will be noted that the fire box is surrounded by water legs 6, 
7, and 8, and the water and steam space 17. Water is also circulat- 
ing around the tubes and is several inches deep above the crown sheet 
18. As combustion takes place in the fire box and the hot gases 
pass through the tubes, the plates of the fire box and the tubes become 
heated. As a consequence, the water in contact with these hot sur- 
faces becomes heated also, and steam is formed which rises to the 
top of the boiler, entering the steam dome H from whence it is taken 
by the pipe 15 through a throttle valve to the cylinder. By using 
a steam dome a better quality of steam is obtained, because it is so 
far above the water level that less water is carried over by the steam 
into the steam pipe 15. 

This type of boiler has many advantages as well as some disad- 
vantages. It has a large amount of heating surface and it is 
well distributed. Due to the large amount of heating surface and 
the excellent draft arrangement, a high evaporation per square foot 
of heating surface is obtained. It is well adapted to various classes 
of service and operating conditions. Its disadvantages consist largely 
in the cost incurred in its maintenance especially in localities where 
bad water must be used. When this condition is imposed upon it, 
the flues give trouble by leaking around the joints where they enter 
the flue sheets 9 and 11. This leakage may at times become trouble- 
some and in the end costly if proper preventive measures are not 
taken regularly. Some criticism is also made of this boiler on account 
of the necessity of using stay bolts in the crown sheet and water legs. 
It must be admitted that stay bolts are also an item of considerable 
expense in bad water districts where high steam pressures are used. 
But by watchful care and manipulation this boiler will give splendid 
results and for some classes of service it has no equal. 

The type of boiler, shown in end view in Fig. 44 and in longitudi- 
nal cross section in Fig. 45, is a modification of the well-known and effi- 
cient Scotch marine boiler. The boiler consists primarily of a cylin- 
drical fire box 1 enclosed by a circular shell. About midway of the 
fire box is placed a bridge wall 7, which deflects the hot gases upward 
against the shell of the fire box. Ordinary cast-iron grate bars are 
inserted as at 4, with the ash pit below. It is to be noted there is 
a water space 6, which extends the entire distance around the circular 
fire box. Above the fire box there are a number of return tubes 3, 



58 



STEAM ENGINES 



which take the hot gases from the rear end 8 of the boiler to the smoke 
stack. The path of these gases is indicated by the arrows. To 
protect the rear sheet from the heat of the gases, a protection plate 
9 is riveted or bolted to the plate. As steam is generated it rises, 
enters the steam dome 12, passes into the steam pipe 13, and onto 
the engine. 

It should be noted that this boiler contains no stayed portions 
and that all the surfaces are circular in form and securely riveted. 

There being no stayed sur- 
faces the circulation of the 
water is not interfered with 
— which is an important con- 
sideration — and the oppor- 
tunity for scale and sediment 
to collect is greatly reduced, 
hence there is less likelihood 
of portions of the boiler be- 
coming heated to the point 
of injuring the boiler or im- 
pairing its safety. Still an- 
other feature of interest in 
the boiler is that the gases 
are made to traverse the en- 
tire length of the boiler twice 
before being ejected at the 
stack. This being the case 
an opportunity is given for a 
greater portion of the heat 
contained in the gases to be 
absorbed by the water, thus 
securing a higher thermal 
efficiency than obtained from boilers of the locomotive type. Having 
no stayed surfaces and a small number of flues results in a small 
maintenance cost of this type of boiler. 

Traction engines run in sizes from about 7 J inches X 10 inches 
to 12 inches X 12 inches for single engines, and for compound 
engines the common sizes are 5f inches X 8 J inches X 10 inches to 
9J inches X 13 inches X 11 inches. The corresponding horsepower 




Fig. 44. End View of Modified Scotch 
Marine Boiler 



STEAM ENGINES 

— f» ■- ** *-, — fls 



59 




60 STEAM ENGINES 

developed will run between 15 and 100. The speed attained on the 
road in miles per hour is about 2\ to 5. 

Road Roller Type. The traction engine just considered as an 
agricultural engine may also be considered as a portable engine or a 
road locomotive. A portable engine is, therefore, one that can be 
easily moved about from place to place, or as in the case of the trac- 
tion engine it may be mounted upon wheels and self-propelled. 




Fig. 46. Semi-Portable Engine and Boiler 

Another illustration of a similar type is the ordinary road roller, or 
road locomotive as it is sometimes called. The principle of its con- 
struction and operation is similar to the traction engine, the chief 
difference between the road roller, or road locomotive, and the ordi- 
nary traction engine being that the two front wheels of the traction 
engine are replaced by a large smooth roller, or cylindrical weight, 
which revolves as the engine moves. The drive wheels of the road 
roller are also made large, heavy, and contain no cleats or lugs. These 
rollers are used in the making of macadamized or other forms of roads. 



STEAM ENGINES 61 

Semi=Portable Type. The semi-portable engine is usually 
connected with a small boiler and the two together may be moved 
from place to place as required. It is not mounted upon wheels but 
rather on large wood skids, and is moved by being placed either 
in a wagon or on rollers. It is largely used for hoisting purposes in 
connection with the construction of large buildings, bridges, etc. 

Since the portable and semi-portable engines have no transmis- 
sion mechanism, they are lighter and considerably cheaper to con- 
struct than traction engines. 

A very neat, compact, and serviceable type of semi-portable 
engine is illustrated in Fig. 46. It is mounted upon skids so that it 
may be easily moved about. The engine is mounted on top of a 
Scotch marine boiler, similar to the boiler last described, and is of 
the plain slide valve, center-crank type, with a centrifugal governor. 
The boiler is equipped with a pressure gauge, water glass, and such 
other appliances as are usually found in a boiler room of moderate 
size. The boiler used is sometimes of the locomotive type and, 
oftentimes, both engine and boiler are of the vertical type. The 
smaller units are usually of the vertical type, the larger ones of the 
horizontal type. The semi-portable plant is built in sizes ranging 
from about 20 to 70 horsepower. If the semi-portable plant, Fig. 
46, be mounted on wheels and drawn by horses or some other means, 
then it is usually classed as a portable engine as distinguished from 
a semi-portable or traction engine. 

LOCOMOTIVE ENGINES 

It is not within the province of this work to fully discuss the 
modern railway locomotive, but suffice it to say that no other power- 
developing unit has been so rapidly developed with such economical 
results. Considering the exacting demands made upon a locomotive, 
its performance is remarkable. The locomotive consists of two pri- 
mary elements, namely, the boiler which generates the steam and the 
engines which convert the energy of this steam into useful work by 
giving motion to the transmission mechanism. 

Boiler. Fig. 47 illustrates a modern locomotive boiler. It con- 
sists of a cylindrical barrel and an enlarged rear end which contains 
the fire box. The fire box is securely fastened in the boiler shell by 
stay bolts and radial stays. A few rows of sling stays are sometimes 



62 



STEAM ENGINES 




STEAM ENGINES 63 

used at the front end of the fire box to allow for expansion and con- 
traction of the sheets. The boiler is divided into three distinct 
departments, as the fire box A, the water space B, and the smoke 
box C. The sheets 4 and 5, which separate these departments, are 
known as the back and front flue sheets, respectively. The flue 
sheets are drilled with holes to receive the flues. 

Flues. In the particular boiler illustrated about 400 2-inch 
flues are used. These flues extend from flue sheet to flue sheet and 
form a passage for the gases to travel from the fire box to the smoke 
box. Surrounding the flues in the space B and surrounding the fire 
box is water, which is vaporized into steam due to the combustion 
of fuel in the fire box. The total amount of heating surface will 
vary from 2,500 to over 4,000 square feet, according to the type and 
size of the locomotive. Of this total amount of heating surface only 
a very small per cent is furnished by the fire box, there being usually 
only about 200 square feet of heating surface contained in the fire 
box. It is evident, therefore, that the flues are a very important part 
of the locomotive boiler. 

Grate Area. The amount of grate area varies from about 40 
to GO square feet. It must be obvious that in order for so small a 
grate area to supply sufficient heat to such a large amount of heating 
surface there must be a very high rate of coal consumption per square 
foot of grate area. A series of tests made at St. Louis during the 
Exposition in 1904 demonstrated that the amount of dry coal fired 
per square foot of grate area per hour varied from 20 to as high as 
130 pounds. These results were obtained from several different 
types of locomotives operated under widely different speeds and 
loads, hence the above figures may be taken as approximating the 
maximum and minimum consumption under ordinary running con- 
ditions. Under these very widely different operating conditions it 
was found that the equivalent evaporation per pound of dry coal 
varied from 6| to 12 pounds, which compares very favorably with 
stationary boiler performance which gives an average evaporation 
of about 8 pounds of water per pound of coal. 

Mechanical Efficiency. The mechanical efficiency of a locomo- 
tive is also very good. Through a long series of tests conducted on 
a well-equipped locomotive testing plant, a mechanical efficiency of 
65 to 85 per cent was obtained. The same degree of efficiency has 



64 STEAM ENGINES 

been obtained in various other tests and under more adverse condi- 
tions. The locomotive is also very efficient in the use of steam. 
The St. Louis tests showed that simple freight locomotives gave an 
average minimum water consumption per indicated horsepower per 
hour of 23.67 pounds. The water consumption per indicated horse- 
power per hour under maximum load was 23.83 pounds, whereas the 
maximum rate was 28.95 pounds. For compound freight locomo- 
tives the average steam consumption was: minimum load 20. 2C 
pounds, maximum load 22.03 pounds, and maximum consumption 
25.31 pounds. The average steam consumption for simple passen- 
ger locomotives was: minimum load 18.86 pounds, maximum load 
21.39 pounds, and maximum consumption 24.41 pounds. When 
these figures are compared with those of the best stationary engines, 
some idea of the economy of the locomotive can be obtained. The 
steam consumption of an automatic, tandem-compound, condensing 
stationary engine with piston valves under full load is about 18 
pounds per indicated horsepower per hour, whereas the compound 
non-condensing locomotive is about 21 pounds. A Corliss engine or 
a medium speed, four-valve simple engine will give a minimum steam 
consumption of about 22 pounds per indicated horsepower per hour 
under full load. A simple freight engine under full load will use about 
23.5 pounds of steam per indicated horsepower per hour. The fore- 
going figures speak well in favor of the economy of a steam locomotive, 
which is operated under conditions unfavorable to the securing of 
good economy. 

Engine Characteristics. The engines used on locomotives may 
be simple or compound; in fact, both are used extensively, although 
the simple type predominates. It is to be noted that the steam 
locomotive is equipped with two separate and distinct engines — one 
being attached to each side of the boiler, and both attached to the 
driving wheels through the medium of the frames, etc. 

The mechanical construction of these engines is quite similar 
to that of the type already described in this work. Certain features 
are made necessary in order to properly tie together the engine, boiler, 
and transmission mechanism. Perhaps the most noticeable change 
in detail is in the construction of the cylinders and valve seats, other- 
>ise there is little variation from the well-established principles of 
engine design. The valves, rods, crossheads, guides, etc., are 



STEAM ENGINES 63 

made of the same high-grade material and constructed in the same 
first-class manner as is required for a good stationary engine. This 
being true, much of the discussion of the steam stationary engine 
and its parts already given is applicable to the engines of a loco- 
motive. There are, however, many perplexing questions that arise 
with reference to the performance and operation of the locomotive 
as a whole that are never encountered in stationary practice, due to 
the unusual and sometimes trying conditions under which the loco- 
motive must be operated. The solution of these problems demands 
a great amount of ingenuity and engineering ability. 

To discuss the various types of locomotives and tell the many 
interesting and important points connected therewith would require 
entirely too much space, so the discussion must be confined to nar- 
row limits. 

Types of Locomotives. There are certain types of locomotives 
common in American practice which have special names. The 
eight-wheel or " American" passenger type of locomotive has four 
coupled driving wheels and a four-wheeled truck in front. The 
"ten-wheel" type has six coupled drivers and a leading four-wheel 
truck. This type is used for both freight and passenger service. 
The "Mogul" type is used altogether for freight purposes; it has six 
coupled drivers and a two-wheel or pony truck in front. The 
"Consolidation" type is used for heavy freight service. It has eight 
coupled drivers and a pony truck in front. There are also a great 
many special types for special purposes. In switch yards a type of 
engine is used which has four or six drivers with no truck. The 
Forney type has four coupled driving wheels under the engine and 
a four-wheel truck carrying the water tank and fuel. This type is 
used on elevated roads largely. "Decapod" engines are a type used 
for heavy freight service, having ten coupled driving wheels and a 
two-wheel truck in front. A tank engine is one which carries the 
feed water in tanks on the engine itself instead of in the tender, 
as in other engines. 

A locomotive of modern design that is being largely used for 
fast freight service and for heavy passenger service is illustrated in 
Fig. 48. It is commonly known as the Atlantic type locomotive, 
having four leading truck wheels, four coupled drivers, and a two- 
wheel trailing truck. The leading truck wheels serve in a guiding 



66 



STEAM ENGINES 




STEAM ENGINES 67 

capacity. This engine is a compound type with piston valves, is 
well designed, is neatly proportioned, and admirably fulfills every 
requirement. 

Compound Type. In connection with the subject of compound- 
ing just mentioned it may be said that in recent years the compound 
locomotive has been found in increased numbers on American rail- 
roads. A type of compound that has given especial good service and 
which is being adopted by many roads for heavy hill climbing duty 
is the Mallett Articulated Compound. The adoption of the com- 
pound locomotive has been due to a general opinion among railroad 
officials that the findings of a committee of the American Master 
Mechanics Association were true, as demonstrated by practice. This 
Committee says of compounding: 

(a) It has achieved a saving in the fuel burned, averaging 18 per cent at 
reasonable boiler pressures. 

(b) It has lessened the amount of water to be handled. 

(c) The tender can, therefore, be reduced in size and weight. 

(d) It has increased the possibilities of speed beyond sixty miles per hour, 
without unduly straining the engine. 

(e) It has increased the haulage power at full speed. 

(f) In some classes of engines it has increased the starting power. 

(g) It has lessened the valve friction per horsepower developed. 

A number of other reasons are given in their report. Notwith- 
standing these facts, however, the compound locomotive has not 
come into very general use on railroads. 

WATER PUMPS 

The subject of pumping engines is a very broad one, and one 
which has received the thought and study of the most eminent engi- 
neers for many decades. From the earliest history of man there is 
gleaned the fact that human ingenuity and skill had been devoted in 
those early times to the perfection of some kind of power pump. 
It would be a difficult matter to mention an industry of any char- 
acter or description but what a pump was needed somewhere in the 
enterprise. It was first used in a large way in the mining industries 
for pumping water out of the mines. Today it is found in all power 
houses, mines, and factories of various kinds. Both the large and 
small cities depend upon it for their water supply. The heating 
and ventilating systems of modern apartment houses and office 



68 STEAM ENGINES 

buildings use the pump, and mention might be made of many other 
instances where the water pump is indispensable. 

There are two general classes of pumps, namely, crank or fly- 
wheel type and direct acting pumps. 

Crank or Flywheel Type. The crank or flywheel type was the 
first form to be developed. These pumps vary greatly both in their 
design and in the details of their construction. They are of vary- 
ing sizes, including some of the largest and most expensive in the 
world. As a general thing they are used in heavy hydraulic enter- 
prises, for furnishing water supply for cities, and in various other 
enterprises where a large and constant supply of water is demanded. 
In this class of pumps or engines the application of the power in the 
steam cylinders in driving the pump plunger or piston varies greatly 
both in design and detail of construction. Long or short beams or 
bell cranks may be used and sometimes gearing may be employed, 
but in all cases the limit of the stroke of the steam piston and of the 
pump plunger is governed by the crank of a revolving shaft. In 
pumping engines it is not absolutely necessary to have a revolving 
shaft, the only requirement being that the piston in the pump cylin- 
der shall be driven back and forth with a plain reciprocating motion 
which may be exactly like that of the steam piston. For this reason, 
in early pumping engines and also in modern engines, the reciprocat- 
ing motion of the steam piston is applied directly, or through a beam, 
to produce the reciprocating motion of the pump piston or plunger 
without the use of any revolving part. Frequently, however, it is 
desirable to use a flywheel so that the steam may be used expansively, 
and in these cases, of course, a revolving shaft must be used. 

Cameron Belt-Driven Pump. The power pump used as an illus- 
tration, Fig. 49, is a belt-driven one. The belt is placed on the pulley 
1 and can be shifted to a loose pulley by the shifter 2, when desired. 
The shaft 4, which is driven by the belt pulley, extends across the 
frame and has attached to it a flywheel 5 and a small gear wheel, 
which meshes with the large gear wheel 3. The gear wheel 3 is keyed 
to the crank shaft 6, hence, when it is driven, the crank shaft is made 
to revolve, which in turn gives a back and forth movement to the 
piston as in the ordinary steam engine. The flywheel 5, attached 
to the revolving shaft, may be of greater or less diameter and weight, 
depending on the condition under which the pump is to be operated, 



STEAM ENGINES 69 

In addition to assisting the crank to pass the dead center at each end 
of the stroke of the piston, it can be employed as a reservoir in which 
any excess energy may be stored at the beginning of each stroke and 
drawn out during the latter part of the stroke, where the force of 
the water column is greater than that of the steam. By this means 
it is possible to use shorter cut-offs in the cylinder than could other- 
wise be permitted; hence, a resulting saving in steam. Many means 
may be used to drive the power pump. While the illustration shows 




Fig. 49. Belt-Driven Power Pump 

one belt driven, yet they are frequently electrically driven, and 
sometimes the revolving shaft is attached to the shaft of a gas or 
steam engine. 

Deep-Well or Mine Pump. For deep-well or mine pumping, the 
cylinders are often set in a vertical position directly over the pump 
cylinder. The piston rod extends from the steam cylinder directly 
below to the pump plunger. Sometimes it is possible to use steam 
expansively in these pumps by reason of the weight of the recipro- 
cating parts. When the weight is sufficient, the steam can be cut 
off before the end of the stroke and the momentum of the parts will 



70 STEAM ENGINES 

be enough to just finish the stroke, consequently these pumps are 
sometimes compounded. They are used only in pumping from very 
deep wells. 

Direct=Acting Type. A direct-acting steam pump is one in 
which there are no revolving parts, such as shafts, cranks, and fly- 
wheels, the power of the steam in the steam cylinder being transferred 
to the piston or plunger in the pump in a direct line through the use 
of a continuous rod or connection. In pumps of this construction 
there are no weights in the moving parts, other than those required 
to produce sufficient strength in such parts for the work they are 
required to perform and, as there is consequently no opportunity 
to store up power in one part of the stroke to be given out at another, 
it is impossible to cut off the steam in the steam cylinder during any 




Fig. 50. Direct-Acting Duplex Pump with Rocker and Bell-Crank Lever 

part of its stroke. The uniform and steady action of the direct-act- 
ing steam pump is dependent alone on the use of a steady uniform 
pressure of steam through the entire stroke of the piston, against a 
steady, uniform resistance of water pressure in the pump; the differ- 
ence between the power exerted in the steam cylinders and the resist- 
ance in the pump governs the rate of speed at which the piston or 
plunger of the pump will move. The length of the stroke of the steam 
piston within the steam cylinders of this class of pumps is limited, 
and is controlled alone by the admission, compression, and release 
of the steam used in the cylinders. 

Duplex Pump with Rocker and Bell-Crank Lever. The direct- 
acting steam pump, Fig. 50, is known as a duplex pump and con- 
sists simply of two direct-acting steam pumps placed side by side. 
The steam pistons are at one end and the water pistons at the other. 



STEAM ENGINES 71 

The steam pressure acts directly on the pistons; no flywheel is used; 
and since the reciprocating parts are comparatively light and there 
is no revolving mass to carry by the dead points, it is evident that 
in the ordinary form there can be no expansion of steam. The 
pump is inexpensive and gives a positive action. It uses a relatively 
large quantity of steam, but for small work the absolute amount is 
not very great. 

On the piston rod of each pump is a bell-crank lever which 
operates the valve of the other pump. There must be a rocker on 
one side and a bell- crank lever on the other, because of the relative 
motion of the valves and pistons. The first piston, as it goes for- 
ward, must use a rocker, because it draws the second valve back. 
The second piston, as it goes back, must use a bell-crank lever because 
it must push the first valve back in the same direction as its own 
motion. The two pistons are made to work a half-stroke apart, 
thus one begins its stroke when the other is in the middle. In this 
way a steady flow of water is obtained, as both pumps discharge 
into the same delivery pipe. In large pumps of this kind, and even 
in some small ones, the motion described above merely admits steam 
to a small auxiliary piston on each steam cylinder, which then moves 
the main steam valve by steam pressure. 

Duplex Pump with Tappet. Some pumps operate the steam 
valve by means of a tappet instead of a rocker and a bell-crank 
lever, Fig. 51. Its construction and operation is as follows: 

A is the steam cylinder; C, the piston; L, the steam chest; F, 
the chest plunger, the right-hand end of which is shown in section; 
G, the slide valve; H, a lever, by means of which the steam-chest 
plunger F may be reversed by hand when expedient; II are reversing 
valves; KK are the reversing valve chamber bonnets; and EE are 
exhaust ports leading from the ends of the steam chest direct to the 
main exhaust and closed by the reversing valves II. 

The piston C is driven by steam admitted under the slide valve 
G, which, as it is shifted backward and forward, alternately connects 
opposite ends of the cylinder A with the live steam pipe and exhaust. 
This slide valve G is shifted by the auxiliary plunger F, the latter 
having hollow ends which are filled with steam, and this, issuing 
through a hole in each end, fills the spaces between it and the heads 
of the steam chest in which it works. Pressure being equal at each 



72 



STEAM ENGINES 



end, this plunger F, under ordinary conditions, is balanced and 
motionless; but when the main piston C has traveled far enough to 
strike and open the reverse valve /, the steam exhausts through the 
port E from behind that end of the plunger F, which immediately 
shifts accordingly and carries with it the slide valve G, thus revers- 
ing the pump. No matter how fast the piston may be traveling, it 




Fig. 51. Section of Pump Cylinder Showing Valve Operated with Tappet 



must instantly reverse on touching the valve 7. In its movement 
the plunger F acts as a slide valve to close the port E and is cushioned 
on the confined steam between the ports and steam-chest cover. 
The reverse valves II are closed as soon as the piston C leaves them 
by a constant pressure of steam behind them conveyed direct from 
the steam chest through the ports shown by dotted lines. 

The motion of the piston C, Fig. 52, is transmitted through the 
rod M to the water piston in the cylinder R. As the piston moves 



STEAM ENGINES 



73 



back and forth, water enters through the intake valves and leaves 
through the discharge valves immediately above, and finally leaves 
through the delivery pipe P. In order to create a more continuous 
flow of water, an air chamber Q is provided. Any sudden variation 
in the pressure in the line is taken up largely by the air chamber. 
It also serves to lessen the effect of water hammer. 




Fig. 52. Section of Duplex Pump with Tappet 



SPECIAL ENGINES 

Under this heading may be placed a large number of engines 
which have been built for a very definite field of usefulness, such as 
various types of fire engines and automobile engines, where steam 
is used as the motive force. Again a number of experimental engines 
have been built, commonly known as freak engines, having peculiar 
construction and design, which never got beyond the experimental 
stage. Rotary engines as well as rotary pumps have been used to 
some extent, but the rotary engines thus far developed have been so 
extravagant in steam consumption that their use has been discon- 
tinued. It is thus seen that under the head of special engines many 



74 



STEAM ENGINES 



of the engines already discussed, as well as an untold number of 
others of more or less merit, may be properly classed. 

The special engines referred to above were not mentioned for 
the purpose of studying them, but rather to indicate that outside 
and distinct from the steam engines classified and considered, there 
are a large number of special types that should not be entirely ignored. 

MARINE ENGINES 

The subject of Marine Steam Engines is a broad and important 
one, and to treat it properly would require one or two volumes the 
size of this one. However, it seems desirable to discuss the subject 
in a very general way in connection with the still broader subject of 
The Steam Engine, and thus give the student a general idea of 
marine engine parts. 

Definition of Terms. Before taking up the subject, it is thought 
advisable to present a brief statement of nautical terms used in 



Slarboord 





Port 
Fig. 53. Plan of Vessel Showing Different Parts 

describing a vessel. Fig. 53 shows a plan of a vessel. The front part 
A is called the bow; the extremity B is called the stern. An object 
placed near the bow is said to be forward; if near the center C, it is 
amidship; and if near the stern, it is aft. An article, if placed so that 
its major dimension is parallel to the line AB, is said to be placed 
fore and aft. Thus the crankshaft of a triple expansion engine of a 
vessel is located along the line AB and is sometimes spoken of as a 
fore-and-aft engine. An article located crosswise of the vessel, that 
is, at right angles to AB, is said to be placed athwartship. To one 
standing on the deck facing the bow, the starboard side is on his right 
and the larboard, or port side, on his left. 

The width of a vessel FE is its beam, and the perpendicular 



STEAM ENGINES 75 

distance from its lowest part to the surface of the water is called the 
draft. The length of a vessel is the horizontal distance between 
perpendiculars drawn at its extreme ends. The displacement of a 
vessel is equal to the weight of water it displaces and is usually 
expressed in long tons. 

The speed of a vessel is usually expressed in knots per hour, but 
is sometimes given in miles per hour. A knot is equal to about 
1J miles. 

Methods of Propulsion. Speaking in a general way, the pro- 
pulsion of a steam vessel is accomplished by causing a mass of water 
adjacent to the ship to move in a direction opposite to that of the 
ship. Motion is imparted to the water in one of the following three 
ways: (1) by paddle wheels; (2) by screw propellers; and (3) by jets 
of water or hydraulic propulsion. 

The oldest of these three forms of propulsion, the paddle wheel, 
is still much used in lake and river steamers and ferry boats; but for 
ocean-going vessels and in many boats on inland waterways, the 
screw propeller has supplanted it. Jet or hydraulic propulsion has 
not proved to be practical and for this reason has never been used in 
commercial work. 

TYPES OF ENGINES 

Beam Type. The first steam vessels were fitted with paddle 
wheels, and as beam engines were the most common, this form of 
engine was used. Its construction, however, was somewhat modi- 
fied for this service. This arrangement of beam engine and paddle 
wheel was used for many years and was applied to ocean vessels as 
well as to small river boats. It is still used, especially in this coun- 
try, on river steamers and some coast steamers. The beam is sup- 
ported by a large A-frame on the deck, and the engines are about on 
a level with the shaft. 

Engines of this type take up rather more room than those now 
in common use, partly because of great size, and also because of the 
shaft and paddle wheels. Another disadvantage is that in heavy 
weather when one paddle wheel is thrown out of the water the other 
is deeply immersed and takes all the strain, so that there is a tendency 
to rack the boat. Then again if the boat is loaded heavily, the pad- 
dle blades are very deeply immersed; while if light, they barely 



76 STEAM ENGINES 

touch the water. It is difficult to handle the engines satisfactorily 
under either condition. 

Inclined Type. The introduction of the screw propeller over- 
came these difficulties very largely and at the same time required a 
high speed engine. At first, the increased speed was supplied by the 
use of spur-wheel gearing, but gradually higher speed engines were 
built and connected directly to the propeller shaft. It was, of course, 
difficult with small width at each side of the shaft to use horizontal 
engines, therefore various arrangements of inclined engines were 
used before the vertical engine was finally chosen by all as the stand- 
ard form for marine work. It is only in recent years that the verti- 
cal engine has become general in naval work and in merchant steamers. 

Vertical Type. In merchant ocean steamers the common form 
has three cylinders set in line, fore and aft, above the shaft, the cranks 
being set 120 degrees apart in order to give a more even turning 
moment. The three cylinders are worked triple expansion, the 
valves being usually of the piston type on the high and intermediate 
and double-ported slide type on the low. Sometimes piston valves 
are used on all the cylinders. Plain slide valves are not suitable 
for high-pressure work of any kind. While steam turbines are used 
to some extent in ocean-going vessels, the majority of ships in this 
service are equipped with high-speed, vertical, multicylinder engines 
direct connected to the propeller shaft. 

Cylinder Arrangement. The different arrangement of marine 
engine cylinders commonly found in service is shown in Figs. 54 to 57. 

Tandem- and Cross-Compound Types. In Fig. 54, A is the 
tandem-compound arrangement with its single crank; B is the cross- 
compound with cranks set 90° apart; and C is the three-cylinder 
compound with cranks set 120° apart. In arrangement C, the high- 
pressure cylinder is sometimes placed between the two low-pressure 
cylinders. 

Triple-Expansion Type. The cylinder arrangement, Fig. 55, 
is found only on the larger vessels, and is spoken of as the triple- 
expansion type. In this type there are three cylinders to each engine, 
and they are called the high-, intermediate-, and low-pressure 
cylinders, each succeeding one being of larger volume than the one 
preceding. Fig. 55 illustrates two arrangements of the cylinders of 
triple-expansion engines. In arrangement A the cylinders follow 



STEAM ENGINES 



77 






Fig. 54. Diagrams of Tandem and Cross-Compound Cylinder Arrangements 
/J B 






Fig. 55. Diagrams Showing Triple-Expansion Cylinder Arrangements 
ft B 





Fig. 56. Diagrams Showing Other Triple-Expansion Cylinder Arrangements 



78 



STEAM ENGINES 



each other in natural sequence; this requires the least length of 
piping. Arrangement B is frequently used, but requires more piping 
than arrangement A. Another common arrangement is to put the 
high-pressure cylinder in the center of the group. In any of these 
systems the cranks would be set at 120°, giving a more nearly uniform 
turning movement to the shaft, since each cylinder will develop 
approximately one-third the total horsepower of the engine. 

Still other arrangements of the cylinders of triple-expansion 
engines are found in Fig. 56. Arrangement A gives the effect of a 
tandem-compound between the high- and the intermediate-pressure 
cylinder and a cross-compound between these two and the low- 
pressure cylinder — an arrangement which results in cranks being 




s 



Fig. 57. Diagram Showing Quadruple-Expansion Cylinder Arrangement 

set at 90° with the consequent uneven turning effect, but it is some- 
times resorted to because of lack of space for all three cylinders in 
line. Arrangement B is a triple-expansion engine, having six cylin- 
ders. Here the volume of one intermediate-pressure cylinder 
is divided among two cylinders, and the volume of one low-pressure 
cylinder among three cylinders. This form is very expensive and is 
not often used. The arrangement requires less floor area than would 
be required for the same power in a three-cylinder engine. 

Quadruple-Expansion Type. The last cylinder arrangement to be 
considered is found on the quadruple-expansion engine. In this type 
the steam goes from the high-pressure cylinder to the first inter- 
mediate, then to the second intermediate, and finally to the low- 
pressure cylinder. The volume of each cylinder is larger than that of 



STEAM ENGINES 



79 



the preceding cylinder. There are many different arrangements of 
cylinders possible with quadruple-expansion engines. Fig. 57 shows 
the arrangement of cylinders in their natural sequence with the four 
cranks set 90° apart, which gives a slightly more even turning effort 




Fig. 58. Section of Typical Vertical Marine Engine 

than is obtained with cranks at 120°, as in the triple-expansion 
engine. 

The idea in the design of a quadruple-expansion engine is to 
produce an engine more economical in the use of steam than is 



80 STEAM ENGINES 

obtained in any other type. With high-pressure steam, say 200 
pounds and over, it gives a better economy in the use of steam than 
does the triple-expansion engine. However, the saving effected in 
the use of less steam is, to a very large extent, offset by an increase 
in first cost, operating cost, and general upkeep. 

Comparison of Marine with Stationary Types. Fig. 22, page 29, 
and Fig. 58 show cross-sectional views of marine engines. In marine 
work many different designs of engines are used. These two views 
are intended to present merely the general features and charac- 
teristics of the marine engine. In comparison with stationary 
engines attention is called to the different form of frame used, lighter 
frames, different details of the connecting rod, and in the latter figure 
the separate crankshaft for each cylinder and the single crosshead 
guide. Also the cylinders are of complicated form and have double 
walls, and the pistons are of a cup shape. These points will be 
brought out more in detail in what follows. 

ENGINE DETAILS 

Cylinder. The general type of steam cylinder for a marine engine 
consists of three distinct parts, namely, the shell, the liner, and the 
cover. 

Shell. In Fig. 59, the shell is the outer casting forming the out- 
side cylinder wall, the lower cylinder head, and the steam ports. 
As its complicated form makes the casting of the shell a difficult 
matter, an iron is used that runs freely in the mould. Sometimes the 
lower cylinder head is not cast integral with the shell, but is fitted to 
it separately like the cover. 

Liner. The liner is the plain cylindrical casting or bushing, which 
forms the inner cylinder wall. Its use is made necessary because 
the metal in the shell is of such composition that it will not wear well 
if the piston is permitted to work directly on it. The material of the 
liner is usually hard, close-grained cast iron. In some cases forged 
steel is used. It is secured to the shell by bolts through a flanged end, 
or by stud bolts. But one end is fastened to the shell, the other end 
being left free to expand under the influence of the higher tempera- 
tures to which the liner is exposed. 

Cover. The cover forms the upper end of the cylinder. Usually 
it is made of steel to combine lightness and strength. Sometimes the 



STEAM ENGINES 



81 



cover is cast hollow so as to form a steam jacket for the cylinder 
head, but more often it is made of a single wall of metal, reinforced by 
radial ribs on the outside. 

Marine Details Re= 
semble Stationary. Many 
of the details of marine 
engines are so nearly like 
those of stationary en- 
gines in essential features, 
and the minor points of 
difference are so varied 
that special mention of 
them will not be made 
here. For illustrations of 
different parts, reference 
may be made to the ear- 
lier sections of this book. 
For example, Fig. 9 shows 
a typical marine piston 
and connection to the 
piston rod; Fig. 14 a 
typical crosshead and 
crosshead pin; Fig. 16 a connecting rod; and Figs. 18 and 19 typical 
main bearings. 

Crosshead Guides. A form of marine crosshead guide, differing 
from that ordinarily used in stationary work, is shown in Fig. 60. 
The crosshead used with this 
guide is known as the slipper type. 
It has but one bearing surface, 
and this runs in the space between 
SS and A . In the guide the plate 
P is bolted to the engine frame 
so that it receives all the cross- 
head pressure when the engine is 
running ahead. For backward motion of the engine the flanges 
FF are provided to receive the thrust. 

Cranks. In marine work side cranks are not used. The con- 
necting rod is always connected between two crank arms. Further- 




Fig. 59. 



Sectional View of Marine Engine Cylinder, 
Piston and Steam Ports 




Fig. 60. Type of Marine Crosshead Guide 



82 



STEAM ENGINES 



more, each cylinder of an engine has a separate crankshaft. These 
separate shafts are bolted together by flanges, as shown in Fig. 61. 
The dotted lines in this figure show how, in large shafts, the center 
is sometimes made hollow. This is done to make a saving in weight 
and to remove inperfect portions usually found in the center. The 




Fig. 61. Portion of Marine Engine Crank Showing Method of Bolting Sections Together 

center of the shaft is the least effective of any part of it in resisting 
twisting forces, and the outside is the most effective. By using a 
little larger shaft, therefore, and removing considerable metal from 
around its center, a shaft of the same strength as a solid one is 
obtained, with a material saving in weight. The crankshafts are 




Fig. 62. Typical Marine Thrust Bearing 

usually all made of the same size, so as to be interchangeable, and thus 
require fewer parts to be kept in stock. 

Bearings. The bearing, Fig. 62, while not part of the engine, 
will nevertheless be discussed at this point. This is called the thrust 
bearing, and is used to relieve the engine of the thrust caused by the 
revolving propeller in screw-propelled vessels. The propeller shaft 



STEAM ENGINES 



s:; 



is turned with the collars C as a part of it. The cast-iron box R 
is secured to the frame of the vessel just aft of the main engines, and 
the cap G is bolted to it, as shown. The collars C press against rings 
B of gun metal or brass and transmit the propeller thrust to them, and 
thence to the vessel. Rings B are split and are prevented from turn- 
ing by the tongue piece F. Holes P are for lubrication and holes A 





Fig. 63. Type of Thrust Bearing in Whieh Provision Is Made for Taking Up Wear 



are provided for water cooling when needed. Water may also be 
circulated through the base. 

Fig. 62 shows the principle of the thrust bearing, but it is not 
much used because no provision is made for taking up unequal wear 
between the brasses. Fig. 63 shows a type of bearing in which pro- 
vision is made for this feature, the wear being taken up by means of 
the nuts fitted to the long screws at either side of the thrust bearing. 



84 STEAM ENGINES 

Thrust Bearing Calculations. The number of collars required 
in any given thrust bearing depends primarily on the total thrust 
that will come on them. There may be a large number of collars of 
small diameter or a small number of large diameter. The experience 
of the designer is usually the determining factor as to the number 
used. 

Knowing the number of collars required, their diameter may be 
computed from the following formulas, in which n is number of 
collars; D is diameter of collars; d is diameter of shaft; P is total 
thrust; and p is safe allowable pressure per square inch of area, which 
is usually taken as 60 pounds per square inch. 

First taking the formula expressing the total thrust, we have 



/ttZ) 2 7Tt/ 2 \ 



and substituting for p the value of 60 pounds per sq. in., there results 
the formula 

P = Q0X~-(D*-d 2 )n 

= 47(D 2 -d 2 )n 
Transposing in the last formula and solving for the value of D, there 
results the equation 



^\K-£ 



47n 

which gives the diameter of collars required for the conditions 
assumed. 

AUXILIARY APPARATUS 

The auxiliary apparatus aboard a ship is far more numerous 
than would be suspected by one not acquainted with it or even by 
one familiar with the apparatus in stationary power plants. The 
general features of some of the more important pieces of apparatus, 
only, will be described. 

Reversing Mechanism. The reversing mechanism of large 
marine engines is so large and heavy and, at times, has to be moved 
so quickly that it cannot be done by hand. Consequently, in some 
instances a small steam power cylinder is attached to the reversing 
gears to move them. This apparatus is called the steam-starting 
gear and is under the control of the engineer. 



STEAM ENGINES 



85 



The action of this gear, Fig. 64, is as follows: When the revers- 
ing lever, or handle, is moved from the mid-position A to B, the rod 
CE is moved to the left. This movement raises the rod //, which is 
connected to the lever fulcrumed at T. As the rod II raises, the rod 




Fig. 64. Details or Steam Starting Gear 

moves downward, thus causing the arm M to move downward and 
the arm N to move to the right. This movement of the arm N and 
pin / causes a corresponding movement to the right of the reach rod 
and link, to which it is connected. Thus it is readily seen that the 
movement of the reversing lever A moves the link slightly and at the 



86 STEAM ENGINES 

same time causes steam to be admitted to the power cylinder, which 
acts on the piston and aids in the movement of the links. 

Condensers. Surface Type. In marine work the surface con- 
denser is used almost exclusively, because with this type the cooling 
water (sea water) does not come in contact with the steam, and the 
latter can then be used over and over in the boilers. Jet condensers 
on ocean vessels would prevent the continued use of the condensed 
steam because of the deposit the salt of the water would leave on the 
boiler tubes and shell. 

Keel Type. In small boats, such as steam launches, the surface 
condenser would occupy much valuable room and add considerable 
weight, so a substitute, called the keel condenser, is frequently used. 
This consists of several rows of copper tubes placed outside the hull 
along the keel of the boat. The engine exhaust enters at one end of 
these tubes, is condensed by the sea water in contact with the outside 
of the tubes, and is then drawn out of the condenser by the air pump 
and pumped back to the boiler. This form of surface condenser 
requires no circulating pump. 

Pumps. Centrifugal Type. The pump most often used on 
shipboard to circulate condenser cooling water is of the centrifugal 
type, driven by an independent engine or motor. The absence of 
valves in this kind of pump is of advantage, as is also the fact that it 
can be run through a greater range of speed and, consequently, give 
greater volumes of water w T hen occasion demands. Oftentimes the 
piping is so arranged that these pumps can draw from the engine 
room bilge and discharge without passing the sludge through the 
condenser. 

Air and Vacuum Types. Of the many kinds of air or vacuum 
pumps used, the one shown in Fig. 65 has been chosen for description 
as being a good example and one easy to understand. The operation 
of the pump is as follows: The inlet E is piped to the outlet of the 
condenser. On the up-stroke of the piston P, a partial vacuum is 
formed below it, enabling the condensed steam and air in E to rush 
through the foot valves F and into the pump cylinder B below the 
piston. After reaching the upper limit of its stroke, P descends, 
producing a slight pressure on the air and water entrained in the 
cylinder, w 7 hich closes the foot valves against the escape of the cylin- 
der contents. As the piston continues, the bucket valves 77 in the 



STEAM ENGINES 



87 



piston are forced open, permitting the escape of air and water to the 
space above. On the next up-stroke this air and water are forced 
out of the air pump through the delivery valves A and the outlet N. 

A small check valve, or pet-cock (not shown in the figure), is 
usually located in the cylinder wall B just below the delivery valves. 
When insufficient air comes through with the condensed steam to 
properly cushion the piston on the up-stroke, this valve is opened to 
provide the required air 

for cushioning. This air ^ 

does not affect the degree 
of vacuum, because it is 
on the discharge side of 
the pump, where pressure 
on the piston is imma- 
terial as regards vacuum 
in the condenser. 

Vacuum is measured 
by gages similar to those 
used for measuring high 
pressures, but calibrated 
to read in inches of mer- 
cury instead of pounds 
per square inch. A col- 
umn of mercury under 
atmospheric pressure will 
stand about 30 inches 
high. Consequently, 
since 30 inches of mer- 
cury is equal to about 15 
pounds per square inch, one inch of mercury will be equal to 15 
divided by 30, or nearly one-half pound per square inch, the exact 
value being 0.49 pounds per square inch. Suppose the vacuum gage 
of a condenser reads 26. This means there has been a reduction of 
pressure corresponding to 26 inches of mercury or 20x0.49, or 12.74 
pounds per square inch. If the atmospheric pressure is 14.7 pounds 
per square inch, then there remains in the condenser 14.7 — 12.74, or 
1.96 pounds per square inch absolute pressure. 

Besides the auxiliary apparatus already mentioned, there are 




Fig. 65. Section of Air or Vacuum Pump 



S8 STEAM ENGINES 

many more on large and small vessels which cannot be discussed 
here, such as machines used for ventilation, forced draft, steering, 
weighing anchor, operating hoists and capstans, compressed air and 
refrigeration machines, and electric lighting. 

PROPULSION 

Process of Starting. When the engines are started and the 
screws or paddle wheels of a ship begin turning, there is no apprecia- 
ble motion of the ship for a short time. During this short time the 
work done by the propellers is all used in overcoming the inertia of 
the vessel. As the inertia is overcome, the ship gradually begins to 
move and increase its speed. As the speed increases, the resistance 
offered to the motion of the ship through the water also increases. 
When all the power of the screws or paddle wheels is used in over- 
coming the resistance of the water to the passage of the ship through 
it, then the ship will be moving along at an approximately constant 
speed. 

Resistance Factors for Ship in Motion. In smooth, quiet water 
the resistance offered to the ship's motion may be divided into three 
elements, namely: (1) frictional resistance of the hull; (2) eddy- 
making resistance; (3) wave-making resistance. 

The most important of these is the frictional resistance, or skin 
friction. The amount of this resistance depends on the area and the 
length of the immersed surface of the hull, the roughness of this 
surface (whether covered with barnacles, sea- weed, etc.), and the 
speed of the ship. 

Eddy-making resistance, which is usually small, is caused by 
eddy currents following just astern of the ship and by the churn of 
the propellers. 

Wave-making resistance is caused by the waves made at the 
ship bow. 

Winds and waves also offer resistance to a ship, but the amount 
of resistance due to these causes is difficult to estimate. 

Variations of Resistance with Speed of Vessel. It has been shown 
by experiment that for a given ship, the resistances vary almost 
directly as the square of the speed, and that the power required to 
overcome these resistances varies almost as the cube of the speed. 
That is, if at a speed of 10 knots an hour a ship encounters a certain 



STEAM ENGINES 



89 



24000 



/6000 



resistance R and requires a certain power P, if the speed be increased 
to 20 knots, the resistance will be increased to R 2 and the power to P 3 . 

Indicated Thrust. 
Indicated thrust is a 
mathematical expression 
denoting the ratio of the 
total work in foot-pounds 
done by the main engines 
to the distance through 
which this force acts. Ex- 
pressed as a formula, this 
ratio becomes 

rn 33,000 XI.H.P. 



1 4000 

















i 
















\ 
















1 


- 














1 


_ 


ft 




B^ 


-^1 

I 


1 
1 

| 




1 

1 

1 1 




1 





-1 

1 

1 


1 

1 


V 

1 

1 


1 1 

1 1 



6 8/0 

5 peed in Knola 



to 



Fig. 66. 



Curve Showing Indicated Thrusts for 
Different Speeds 



pN 

where T is indicated 

thrust in pounds; I.H.P. is indicated horse-power of engines; p is 
pitch of screw in feet; and N is number of revolutions per minute. 



Since/. II. P. = 



2 PLAN 

33,000 



, this formula may be reduced to the form 



T = 



2 PL A 

V 



Where P is equivalent mean effective pressure in pounds per square 
inch; L is length of stroke in feet; and A is area of low-pressure 
piston in square inches. 

Example. What is the indicated thrust of a 1200 I.H.P. marine engine 
driving a propeller of 20-foot pitch at 90 r.p.m.? 
Solution. 

T _ 33,000 I.H.P. 
pN 
33,000X1200 
20X90 
= 22,000 pounds 

The indicated thrust for any given ship may be taken from a 
curve, such as is shown in Fig. 66. 

Economical Speed. The most economical speed of a ship is that 
speed at which it can travel a given distance with the least consump- 
tion of fuel. At speeds either above or below this particular speed, 
the fuel consumption will be increased. To determine the most 



90 



STEAM ENGINES 



economical speed, the amount of coal used at different speeds is 
determined by trial. These amounts are then plotted, as shown in 
Fig. 67. As it stands, this curve shows merely the coal consumed at 
different speeds, but by drawing a line from tangent to the curve, 
the most economical speed is found at the point of tangency, or in 
this case at N, or about 8 knots per hour. If the coal used by the 
auxiliary machinery is to be considered, then OX, the amount of 
this coal, is laid off as shown, and the tangent drawn from the new 





AW b(J 




L_ 




t 




t 








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X ? 4 6 8 /O /? /4 /ff jff 

5peed in Knob per Hour 

Fig. 67. Curve Plotted to Show Most Economical Speed of a Ship 

origin at X. This new line, tangent at L, gives a higher speed for the 
most economical one than that given for the main engines only. 



PROPELLERS 

Although propellers are not, strictly speaking, a part of marine 
engines, yet the two are so closely related that a brief discussion 
at this point seems desirable. Screw propellers only will be considered, 
because they are used more extensively than any other device for 
propelling vessels of various kinds. 

Details of Screw Propeller. A screw propeller is a set of blades, 
usually constructed of iron or bronze, which are made to revolve in 
the water at the stern of the ship, by being connected to an extension 
of the main engine shaft. 



STEAM ENGINES 



91 



Small propellers are usually cast with the hub and blades in 
one piece, but large ones have a central boss to which the blades are 
bolted. Propellers are made of a variety of metals, including iron, 
steel, bronze, and gun metal. 

Blades. The general appearance of a blade may be seen from 
Fig. 68. Propellers may have two, three, or four blades. In merchant 
vessels the latter is most common. 

Pitch. The pitch of a screw propeller 
is the distance in the direction of the axis of 
the screw that would be traveled by a point 
on the blade during one revolution if there 
were no slip. It is similar to the pitch of an 
ordinary lathe feed screw, but of course is 
much larger. 

Diameter. The diameter of a screw 
propeller is simply the diameter of a circle 
described by the extreme ends of the blades. 
The ratio of the diameter to the pitch of 
a propeller is ordinarily from 1 to 1.1 and 
up to 1 to 1.5. Thus for a 14-foot diameter 
propeller the pitch would likely be from 
14X1.1 = 15 feet to 14X1.5 = 21 feet. 

Propelling Action of Screw Propeller. 
When a screw propeller is revolving in a 
given direction (for go-ahead motion for 
instance), the blades press on the water as 
the threads of an ordinary screw do upon 
the threads in the nut. The pressing of the 
blades on the water causes the water to be 
driven backward. There is, however, a 
reaction caused by projecting this mass of 
water sternward which results in the ahead 
motion of the boat. The useful work done by the propeller is the 
work which forces the water directly sternward; of course, the 
movement of water in any other direction than sternward results 
in a waste power. 

If the screw worked in an unyielding medium, it would advance 
a distance equal to its pitch at each revolution. Hence, the speed of 




Fig. 68. Typical Shape of 
Propeller Blade 



92 STEAM ENGINES 

the screw per minute is the product of the pitch and the number of 
revolutions per minute. 

Example. Suppose a screw is of 18-foot pitch and makes 72 revolutions 
per minute. What is the speed of the screw in feet per minute and knots per 
hour? 

Solution. 

18X72=1,296 feet per minute 
1,296X60 = 77,760 feet per hour 

' un = 12.78 knots per hour 
o,OoO 

Slip. Water is a yielding medium and for this reason the pressure 
of the blades causes the water acted on to be driven back instead of 
remaining firm. Then the actual speed of the ship (when referred to 
the undisturbed water at a slight distance from the ship) is less than 
the speed of the screw. This difference is called slip. Slip is the 
difference between the speed of the screw and the speed of the ship, 
relative to still water. It is expressed in feet per minute and as a per 
cent of the speed of the screw. 

Example. A ship is moving at the rate of 16 knots per hour. The 
screw has a pitch of 19 feet and makes 97 revolutions per minute. What 
is the slip? 



Solution. 



19X97 = 1,843 feet per minute = speed of screw 
' = 1,621 feet per minute = speed of ship 

Slip = 1,843 -1,621 =222 feet per minute 

999 
= -^ = .1204 = 12.04 per cent 
l,84o 

This may be expressed algebraically as follows : Let S equal speed of 
screw; s equal speed of ship; and L equal slip in feet per minute. 
Then 

L = S-s 

S — s 

— — X 100 = slip expressed in per cent 

o 

The slip thus found is not the actual slip, but the apparent slip. 
It is not the actual or real slip, because the screw does not act in still 



STEAM ENGINES 93 

water, but in water that has been set in motion by the screw itself or 
by the hull. 

While the hull moves through the water, it sets in motion the 
water in contact with it, the direction being the same as that of the 
ship. The water close to the ship has a greater forward velocity than 
that at a distance. Since this w r ater has a velocity a little less than 
that of the ship, it soon falls behind the hull and is found at the stern. 
Thus the water in which the propeller acts has a forward velocity. 
Also the velocity is influenced by the waves and eddies, due to the 
lines of the vessel. On account of the many conditions that make the 
velocity of the wake variable, it is difficult to calculate it. 

When the propeller is considered, it is evident that the condition 
of the water in which it works should be considered. Since the 
velocity is difficult to obtain, the real slip is not easily found. 

When slip is referred to, it is generally the apparent slip that is 
intended and not the real slip. The apparent slip varies from 5 to 25 
per cent — 15 to 20 per cent being a fair average. The actual slip is 
usually from 5 to 15 per cent greater than the apparent. 

MANAGEMENT OF MARINE ENGINES 

It is of great importance that the chief engineer and all of the 
assistants should be familiar w T ith the machinery of the ship. The 
steam and exhaust pipes, both main and auxiliary, and the location of 
the valves should be carefully traced; also the feed pipes to the 
boilers, and the piping to the condensers. It is important that each 
officer should know the function of every pump and the piping from 
the bilges. Unless the engineer on watch is well acquainted with all 
the machinery, he cannot act promptly in case of emergency, but will 
be compelled to send for the chief or find someone under him who can 
furnish detailed knowledge of the part in question. The promptness 
and confidence with which he can act at all times depend upon his 
knowledge of all the parts of the machinery. 

Before Starting. Just what to do before starting depends largely 
upon the prevailing conditions and the arrangement of the machinery. 
In general, the following should be observed : 

All gear used in port or for repairs should be stowed away and all covers 
replaced. Such valves as the inlet and the outlet valves of the circulating pump 
and all valves to bilge pipes should be tried and put in proper condition. The 



94 STEAM ENGINES 

outboard delivery valves from all pumps should receive especial attention. The 
valves to jackets and the bulkhead and regulating valves should be opened and 
inspected. The valves in the main steam pipe should not be closed tightly or they 
will be set fast when steam enters. 

The oil cups and lubricators should be examined and put in good working 
order and the necessary worsteds adjusted. 

The various joints should be inspected and the glands packed. 

Pressure and vacuum gages should be connected and the shut-off cocks 
tried. 

The bright parts of the machinery that are likely to become splashed with 
water should be oiled. 

Auxiliary engines should be tried by steam if possible; if not, by hand. 
Such auxiliaries as the steering engine, circulating engines, and the electric- 
lighting engines should receive careful attention. In all cases, the reversing 
engine should be tried before using the main engines and before entering port it 
should again be tried to make sure that it works properly. 

The main engine should be oiled at all the rubbing and rotating parts. 

An important item is the examination of the crank pits and all the working 
parts. If these parts are not examined, some obstruction may prevent the engine 
from starting. The main engines should be turned through at least one revolu- 
tion, both ahead and astern, by hand. 

In case forced draft is used with closed stokeholds, the draft gages should 
be cleaned and filled with water and the air-tight doors should be examined and 
rigged. The fans should be carefully oiled and adjusted. 

To Start Engine. In starting an engine the engineer in charge 
must use the knowledge gained from experience, as no set rules will 
apply to all engines. For instance, a small single-cylinder engine is 
not started in the same manner as a large triple-expansion engine. 
In the following we will consider the types of machinery most used — 
the triple-expansion engine and surface condenser. 

In general, to start an engine it is first necessary to warm the 
cylinders and form a vacuum in the condenser; the engine can then 
be started by admitting steam to the cylinders. 

To Form Vacuum. It is usual to fit an independent circulating 
pump, so the Kingston or sea-valve should be opened and the dis- 
charge valve tested to see if it lifts readily. The circulating pump is 
then started so that the condenser will not become heated by the 
drains and exhaust steam. The auxiliary air-pumps should then be 
started to keep the main and auxiliary condensers free from water and 
to form a partial vacuum. If the air-pump for the main condenser 
is independent, it may be started so as to form a vacuum. 

To Warm the Engines. To warm the engines, all cylinder, 
receiver, and steam chest drains are put in communication with the 



STEAM ENGINES 95 

condenser. In order to ascertain whether or not the drains are work- 
ing properly, a by-pass arrangement is often fitted. This arrangement 
connects the drains to the bilges. The jackets are usually trapped to 
the hot well or feed tanks, but can be drained directly to the bilges. 
If all the drains are in order, open slightly the throttle valve and all 
valves in the main steam pipe. This will admit a little steam to the 
high-pressure steam chest. Steam is also admitted to the jackets to 
assist in warming the cylinders. 

Now open the by-pass valves a little to admit steam to the 
receivers. The steam in the receivers finds its way into the cylinders 
and helps in the warming up. To warm both ends of the cylinders 
move the valve gear back and forth slowly from full gear ahead to 
full gear astern. The throttle may now be opened a little wider, 
enough to set the engine in motion. By means of the reversing gear, 
the cranks can be made to move back and forth without making a 
complete revolution. 

Opening the Throttle. We will assume that the engine is thor- 
oughly warm and (as the drains are open) free from water. Steam is 
in the jackets and the starting engine and starting valves ready. The 
centrifugal pump is at work circulating water through the condenser 
and either the auxiliary air-pump or an independent air-pump is at 
work. 

To start the engines, run the links into full gear ahead or astern 
and open the throttle valve. In case the engines do not start, use the 
by-pass or auxiliary starting valves. The engines should be started 
slowly and the speed gradually increased by admitting more steam. 
After the engines have made 200 revolutions or more, the drain cocks 
may be closed. 

Causes of Failure to Start. Marine engines may fail to start from 
many causes, but if proper precautions are observed before trying to 
start there should be no difficulty. Among the causes which are not 
apparent from the exterior are: 

The throttle valve spindle may be broken. 

The high-pressure valve (if a slide valve) may be off its seat ai;d 
admit steam to both ends. 

The engine may be gagged; that is, the throttle will supply 
steam to one side of the high-pressure cylinder and the by-pass valves 
admit steam to the opposite side of the intermediate or low. In this 



96 STEAM ENGINES 

case the engine will not move, as the pressures are equalized. In 
using the by-pass valves, the valve or valves should be used which 
will produce a turning moment on the shaft. Let us suppose that 
both the high- and low-pressure valves cover the ports, and the inter- 
mediate slide valve is in such a position that steam can enter that 
cylinder. If now the throttle is opened, the engine will not start, 
because both ports are closed. If the by-pass valves to both receivers 
are opened, steam will be admitted to the proper side of the inter- 
mediate piston. Also the steam in the low-pressure receiver will find 
its way through the exhaust cavity of the low-pressure slide valve to 
the other side of the intermediate cylinder. The result will be that 
the engine will not start because the high and low are not available 
for starting and the pressures on the intermediate piston will balance. 
In this case steam should be admitted to the intermediate receiver 
only. If steam is admitted to the low-pressure receiver only, it tends 
to force the intermediate valve off its seat. 

The opening of the wrong starting valves will frequently produce 
a similar situation. 

If the engine has become gagged, it should be freed from steam. 
This may be done by closing the throttle and moving the link 
to the opposite extreme position. The engine can then be started 
in this direction and then be quickly reversed; or it may be 
started in the proper direction if the mistake is not repeated. 
In case the engine will not start, one of the following conditions 
may be the cause: 

(a) The valve stem may have become broken inside the chest or the 

valve may have become loose on the stem. 

(b) One of the eccentrics may be broken or slipped on the shaft. 

(c) Bearings set up too tightly or too much compression on the 

packing in stuffing boxes often prevent starting. 

(d) The propeller may be fouled by a rope or other obstruction. 

(e) The turning gear may not be disconnected; that is, the worm 

may still be in gear with the worm wheel. 

Adjustments After Starting. After the engine has been running 
for a short time, the following adjustments should be made: 

The speed of the feed pumps to maintain the proper water level 
in the boilers. 

The supply of circulating water to the condensing equipment. 






STEAM ENGINES 97 

The amount of circulating water around the main bearings should 
be reduced as low as possible to relieve the work of the bilge pumps. 

The pressures in the steam jackets and the valves in the drains 
should be regulated. 

Lubrication. The oil cups on bearings require special attention. 
The caps of lubricators should be kept in place on the oil cups to 
prevent dirt and water from entering. The lubricators should be 
examined frequently because the pipes and passages are likely to 
become clogged. 

For cylinder lubricator as little oil as possible should be used, so 
as to keep the boilers free from grease. The lubricators used for this 
work are discussed and described in "Steam Engines", Part II. 

Hot Bearings. There are many causes for hot bearings, the most 
common of which is dirt. To prevent the accumulation of dirt in the 
bearings, the engine room, oil cups, and pipes, should be kept clean. 

Insufficient and improper lubrication will almost always cause 
heating. If the oil enters at the top, where the pressure is greatest, 
suitable oilways should be cut to allow the entrance of the oil. 
Another method is to lead the oil to a point of low pressure. 

Other causes are improper adjustment or alignment and deficient 
surface. These defects lead to excessive pressure in some parts, which 
causes heating. 

In many large, modern engines, the main bearings have the 
castings cored out so that water circulates through the bearing con- 
tinuously, but does not come in contact with the rubbing surface. 
In the caps there are holes to allow the hand to feel of the bearings 
and to allow air to circulate. The temperature of the circulating 
water and the hand test indicate the condition of the bearing. 

In case a bearing tends to become too warm, the amount of 
circulating water is increased. In extreme cases of heating, the 
bearing may be flooded with water, thus washing out all of the dirt 
and reducing the temperature. If this water douche is used, plenty 
of oil should be supplied and the bearing given careful attention. 

It may be necessary to slack back the nuts on the caps for a 
short time, but they should be slacked but little or there will be 
pounding. Sometimes the power distribution may be temporarily 
altered, that is, the power given out by any one cylinder may be 
decreased, and the power given out by the others increased by running 



98 STEAM ENGINES 

the link in or out and adjusting the expansion gear. It may even be 
necessary to reduce the speed for a time, but this is not done unless 
necessary, as it causes delay. 

If the bearing is discovered to be hot, the water service should 
not be applied, as the sudden cooling may cause fracture. In this 
case the engine should be slowed down or stopped and the bearing 
cooled with oil, sulphur, or a mixture of soft soap, water, and oil. 

Bearings that are lined with white metal should receive special 
attention, as the white metal soon becomes plastic and melts at 
about 400° F. 

The water douche should be used only in extreme cases and with 
caution, because it may cause fracture and is likely to corrode and 
destroy the bearings. If water must be used, the parts should be 
cleaned and oiled as soon as the engines stop. 

Hot Rods. Piston rods and valve rods are often kept lubricated 
by means of a large brush, called a swab. Frequently in starting, a 
man with a swab is stationed to keep the rods cool. If these rods 
become warm because of tight glands, they may be cooled by slacking 
back the gland and applying water and oil by means of a swab or 
syringe. If the rod is hot and water is applied, one side may be 
cooled and shortened; the result will be a bent rod. Instead of using 
water, the engines should be eased. If the rod cannot be felt, a few 
drops of oil or water syringed on the rod will show whether or not it 
is hot. If hot, the water will hiss or the oil will burn and cause 
smoke. 

As with bearings, piston rods that are packed with metal packing 
should receive careful attention, as the packing may run and cut the 
rods. The principal causes for hot rods are glands too tight or not 
properly packed, piston rod not in line, and insufficient lubrication. 

Knocks. Bearings should be adjusted while the engines are 
running. If a bearing is loose, it will knock at both ends of the 
stroke. Usually knocks can be located by the sound or by the feeling. 
Knocking in the cylinder may be due to a loose or broken piston ring, 
piston loose on the rod, or a nut or bolt loose. If knocking occurs, 
open the cylinder and jacket drains to be sure it is not due to an 
accumulation of water. If the noise continues at various speeds, it 
is probably due to looseness of the piston rings. If this is the case, 
the ring must be re-scraped and fitted, 



STEAM ENGINES 99 

Jackets. The pressures in the jackets should be maintained at 
the desired amount. The jacket drains are led either to the condenser 
or to the feed tank. If led to the feed tank, the temperature of the 
feed water is then raised. The jackets should be well drained, as 
water causes a crackling noise at each stroke. The remedy is to open 
the drains wide and, when clear of water, regulate the drain valves 
by increasing the opening. 

Bilges. The bilge pumps should be at work constantly while the 
vessel is steaming, so that water will not accumulate in the bilges or 
crank pits. The crank pits should not be in communication with 
the bilges, or the oil from the crank pits will be spread over the 
bilges. If the stokehold bilges empty into the engine room bilges, 
the bilge water should be strained on account of the fine coal in the 
stokeholds. Strainers should be carefully attended to, as fine coal, 
waste, and articles carelessly left in the bilges are likely to choke them. 
It is considered good practice to pump from wells formed in the bilges 
and covered with strainers. 

Linking Up. When starting, the links are placed in full gear. 
When running at the required speed, the engine is linked up so that 
the expansive working of the steam may be utilized. The best 
position of the links for a given speed is determined by experience. 
Trial will show at what position the engine will run smoothly, 
economically, and without too much noise. The throttle valve should 
be wide open, so that steam will enter the high-pressure chest at 
nearly boiler pressure. If the engine is running at reduced speed, it 
is a good plan to link up the high-pressure engine by the use of the 
block in the slot of the arm on the weight shaft. This will increase 
the total ratio of expansion, but will not reduce the port opening of the 
intermediate- and low-pressure cylinders. If there is any probability 
of a change in speed, the engineer in charge should see that the start- 
ing engine is warmed and drained from time to time and be sure that 
it is ready for use. Grunting of the slide valves is sometimes stopped 
by running the links into full gear for a short time, then adjusting 
them in a slightly different position. 

Marking Off Nuts. In order to have a record of adjustments 
and to aid in adjusting bearings, the following marks are made. At 
each corner of the hexagonal nut near the face that bears on the 
washer, a number is stamped, as shown in Fig. 69. The washer is 



100 



STEAM ENGINES 



TT 



TI'I'I'ITI'I 



prevented from moving by some device. A part of the circumference 
of the washer is marked off in, say, 10 divisions about one-half inch 
apart. These divisions are then sub-divided and numbered. It is 
then easy to record the position of the nut by noting what number on 

the washer coincided with the corner 
of the nut. Thus 1 on \\ or 2 on 8J. 
Refitting Bearings. To find out 
whether or not a bearing needs refit- 
ting and to ascertain the amount of 
play, a lead is taken. The cap is first 
removed and a piece of lead wire is 
laid along the journal parallel to the 
axis. Some engineers place two pieces 
around the journals near the ends and 
others place them diagonally. The 
cap is then replaced and screwed down 
The cap is again removed and the leads taken 
They should be flattened uniformly. The 
If the marks on the nuts at which 




J 



Fig. 69. Marking Nuts and Washers 



hard on the liners. 

out and examined. 

thickness shows the clearance. 

the leads were taken are noted, they may be compared with the 

marks and leads taken sometime afterward and the location and 

extent of wear known. 

If the leads show that the bearing needs refitting, the caps are 
first removed and the journal, caps, and oilways cleaned. The 
journal is then carefully calipered and, if found oval, cut, or rough, 
should be filed all over until smooth and true. This process requires 
considerable care and skill for the new surface must be concentric 
with the axis. The filed surfaces are smoothed by an oil stone or 
emery. If emery is used, care must be taken to clean all surfaces. 

After the journals are in proper condition, the brasses, if used, 
are fitted by filing and scraping. A little red lead smeared on the 
journal will assist in the fitting. The brasses should be eased away 
at the sides, as the metal at those points is of no assistance, but 
increases the friction. 

If the bearings are lined with white metal, they must be relined 
when the white metal is worn through. To do this a mandrel of the 
same size as the journal is placed in position in the bearing and the 
molten metal poured in or the strips of white metal are hammered 



STEAM ENGINES 101 

into the recesses. The metal stands clear of the brass about J inch 
when finished. 

Stopping the Vessel. Before Entering Port. When near port, the 
fires should be burning light, so that there will be no difficulty in 
keeping the steam pressure down. If the pressure rises when the 
engines are slowed down, there may be an unnecessary waste of fresh 
water on account of the blowing of the safety valve; the loss of fuel 
will also be considerable. 

Before entering port all the ashes should be dumped overboard 
and all the water possible should be pumped out from the bilges. 
The reversing and capstan engines should be warmed ready for use. 
When the engines are slowed down, the w r ater service should be shut 
off and the cil supply increased to prevent rusting of the bearings 
while in port. The pressures in the receivers and jackets should be 
watched, as they have a tendency to rise w 7 hen the engines slow down. 

Adjustments After Stopping. When the engines are done w 7 ith, 
the valves in the main steam pipe and the jacket valves should be 
closed, but not too suddenly; the steam should then be allowed to 
escape from the pipe or used up by the reversing or other auxiliary 
engine. All drains and receiver relief valves should then be opened, 
and the steam should be shut off from the steering and reversing 
engines. 

The hand-turning gear may be put in gear as soon as there is no 
steam left in the engine room main steam pipe. The engines should 
now be cleaned w T hile warm by wiping down the rods and shafting 
with cotton w r aste and oiling the bright parts to prevent rusting. 

In case the engines are stopped suddenly, notice should be 
immediately given in the fire room so that the draft may be checked 
and the evaporation reduced. If the water level is low T , water should 
be pumped into the boilers. Every precaution should be taken to 
prevent an oversupply of steam, but if it is impossible to prevent the 
rise of pressure, the excess of steam may be used in the evaporators, 
distillers, etc., and in pumping out bilges and crank pits. The engines 
should be kept warm and well drained so as not to cause delay in 
starting. If the air-pump is worked by an independent engine, it 
should be kept working for a time, so that the condenser will not be 
flooded with water and injure the air-pump. If the air-pump is 
worked from the main engine, it will of course stop as soon as the 



102 STEAM ENGINES 

engines stop; in this case put on a feed-pump to keep the condenser 
free from water. The circulating engines may be stopped soon after 
the engines stop. 

As in case of entering harbor, watch receiver and jacket pressures, 
and stop the supply of water to bearings, etc. If there is any chance 
of starting again soon, keep the reversing engine warm and well 
drained. 

Precautions for Long Stay in Port. If the stay in port is to be 
long, the main condensers and air-pumps should be well drained and 
several of the boilers may be cleaned and repaired if necessary. The 
fires should be allowed to burn themselves out gradually. If the stop 
is for a short time, the fires should be banked. 

Emergencies. What to do in emergencies depends upon the 
arrangement of the machinery. The kind and number of engines 
and their arrangement and capacities of the condensers and auxiliary 
machinery often determine what course to pursue in case any part 
breaks or gets out of position. 

Cylinder Head Broken. If a cylinder head breaks, it should be 
repaired if proper means are at hand. If it cannot be repaired, the 
steam port which admits steam to that end may be blocked up by 
driving in plugs of soft pine and the engine run single-acting. This is 
comparatively simple if the valve is a plain slide, but with a piston 
valve the many ports make it more difficult. If a cylinder head of a 
triple-expansion engine breaks, and one engine must run single-acting, 
the expansion gear should be arranged so that the work will be 
properly divided. 

Fracture in the Crankshaft. What to do in this case depends upon 
many conditions. If the engine is of the multicylinder type, and the 
crankshaft is made in interchangeable lengths, fit the spare length 
in place of the disabled one. In case no spare length is carried and 
the crankshaft of the low-pressure engine is damaged slightly, change 
the low-pressure length to the high-pressure engine and place the 
high-pressure length in place of the low. The low-pressure length 
transmits the most power. If the damage is considerable, such as 
the breaking of the crankpin, the length cannot be used and the 
high-pressure engine must be disconnected. If the pumps are worked 
from the high-pressure crosshead, repair the broken shaft, place it 
in the high-pressure engine, and block up the steam ports to the 



STEAM ENGINES 103 

high-pressure cylinder. The power is then developed in the inter- 
mediate- and low-pressure cylinders; the amount of power trans- 
mitted to the high-pressure crankshaft being just sufficient to work 
the pumps. Probably it will be necessary to run the engines slowly 
because of the weak shaft. 

Piston Broken. If the piston, piston rod, or valve stem become 
broken and cannot be repaired, the damaged engine must be dis- 
connected and the power furnished by the others. 

Air-Pump Broken. In case the air-pump breaks and cannot be 
repaired, the exhaust may be carried to the deck and the engines 
run non-condensing. This is a great disadvantage if the amount of 
fresh water carried is slight and the ship is far from port. In case no 
separate exhaust is possible, the auxiliary air-pumps may be con- 
nected and the ship proceed. In most cases, however, the auxiliary 
air-pumps are not of sufficient capacity to remove all of the con- 
densed exhaust steam and the air; therefore, no vacuum will be 
carried, but the condensation may be returned to the boilers. 

Bent Piston- Rod. In the case of a small rod and a long, slight 
bend, the rod may be straightened by placing it in a lathe and 
applying a powerful lever. A large rod, or one with a quick bend, 
should be heated to a dull red in a wood fire. The rod is then placed 
in a large lathe and straightened by an hydraulic jack. In doing this 
work care must be taken that the rod is not heated too hot, does not 
scale, and that the points of contact are protected by copper plates. 

Eccentric Broken. If the go-ahead eccentric or eccentric rod 
breaks and cannot be repaired, the go-astern eccentric can be shifted 
in its place. The engine will now run ahead, but cannot be reversed. 
The go-astern end of the links must be kept from dropping by some 
flexible support, such as a rope or chain. 

Another method is to disconnect the connecting rod from the 
crankpin and crosshead of the disabled engine, and block up the 
steam ports so that the steam will flow to the other cylinders by the 
shortest passage. The piston should be secured on the bottom of the 
cylinder. The valve should be removed. After removing the 
broken valve gear, the engine is ready to start. This method may be 
used if the pumps are worked from the low-pressure crosshead and 
the low-pressure engine is intact. If, however, the high-pressure 
eccentric is broken and the pumps are worked from that crosshead, 



104 STEAM ENGINES 

the same method may be pursued as described for a fractured crank- 
shaft. That is, the valve gear should be removed, the ports blocked, 
and the piston, the piston rod, crosshead, and connecting rod left in 
place. The moving parts of the high-pressure engine will then work 
the pumps by means of the power transmitted to the high-pressure 
crank. The engine must be run slowly, but can be reversed. 




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STEAM ENGINES 

PART II 



MECHANICAL AND THERMAL EFFICIENCY 

The brief historical review and the study of the various types 
of engines have served to unfold the degree of perfection that 
has been attained in the design and details of construction of the 
modern steam engine. From a mechanical standpoint, the mod- 
ern engine is highly efficient. A mechanical efficiency, that is, 

- — - 11 > °f from 85 to 95 per cent is not infrequently 

Indicated horsepower 

obtained. An actual test of a 12-inch Xl9f-inchX 15-inch tandem- 
compound Corliss engine operating non-condensing gave a mechan- 
ical efficiency of 94 per cent. That is to say, if the engine was 
developing 120 horsepower in the cylinders, that 112.8 horsepower 
would be delivered by the engine to the flywheel. In other words, 
the horsepower used in overcoming the friction of the various moving 
parts was only 7.2 or 6 per cent of the total horsepower developed. 
Low Thermal Efficiency Inherent. From the standpoint of 
thermal efficiency, however, the modern engine is very inefficient, 
but it is much more efficient than the older types. Even the maxi- 
mum thermal efficiency obtained is only about 15 per cent, and, 
under favorable conditions, this very low figure may be so reduced 
that the engine is operated at a great economic loss. It is now 
proposed to briefly point out some of the causes for the very low 
thermal efficiency obtained and to indicate some of the means that 
have been employed to increase the thermal output of the steam 
engine. In order to make this study it becomes necessary to again 
refer to steam and its properties. It is well known that steam 
contains a great deal of heat, and that this heat can be converted 
into useful work by allowing the steam to pass from the high tem- 
perature of the heat generator to the lower temperature of the 
refrigerator, during this change giving up heat. There are several 



106 STEAM ENGINES 

# 

forms of heat engines, all of which convert the heat contained in 
some substance into work. The theoretically perfect engine shall 
be considered first, and after that the modifications that go to make 
up the steam engine of today. 

Ideal Engine. The theoretical engine, Fig. 70, is supposed 
to receive heat from the generator at constant temperature 7\ until 
communication is interrupted at B. The working substance expands 
to C without losing or gaining any heat from external sources until 

the temperature of the refrig- 
erator is reached. The engine 
now rejects heat at the constant 
temperature T 2 of the refrigera- 
tor and then compresses the 
working substance without loss 
or gain in the quantity of heat 
until the temperature of the 
heat generator is reached. These 
are ideal conditions and, if ful- 
filled, the efficiency of the per- 
fect engine will depend only on the difference between the tempera- 
ture at which heat is received and rejected or, in other words, it 
depends only upon the difference in temperature between the gen- 
erator and the refrigerator. 

If T\ equals the absolute temperature of the heat received 
and T 2 equals the absolute temperature of the heat rejected, then 
the thermal efficiency E of the engine will be represented by the 
formula 




Fig. 70. Theoretical Indicator Diagram 



E = 



2\ 



Or, in other words, the efficiency equals the absolute temperature 
of the heat rejected, subtracted from the absolute temperature of 
the heat received, and the remainder divided by the absolute tem- 
perature of the heat received. 

Example. Given an engine using steam at a 120 pounds absolute pressure, 
and exhausting at atmospheric pressure. What is the thermal efficiency? 

Solution. The absolute temperature corresponding to 120 pounds 
pressure is 341.31 + 459.5, or 800.81°, and the absolute temperature of the 
exhaust is 212 + 459.5, or 671.5°. Then 



STEAM ENGINES 107 

800.81-671.5 



E 



800.81 
.161, or 16.1 per cent 



Losses in Practical Engine. In General. In actual engines 
this efficiency can not be realized, because the difference between 
the heat received and the heat rejected is not all converted into use- 
ful work. Part of it is lost by radiation, conduction, condensation, 
leakage, and imperfect action of the valves. The cylinder walls of 
the theoretical engine are supposed to be made of a non-conducting 
material, while in the actual engine the walls are of metal, which 
admits of a ready interchange of heat between cylinder and steam. 
This action of the walls can not be overcome and is so important 
that a failure to consider its influence will lead to serious errors in 
computations, and no design can be made intelligently if based on 
the theory of the engine with non-conducting walls. In theoretical 
engines steam expands without the loss of any heat, while in the 
actual engine a large amount of heat is lost by radiation. There is 
also a considerable loss of pressure between the boiler and the engine, 
due to the resistance offered by the pipes and cylinder passages. In 
a slow-speed engine with large and direct ports and valves this 
trouble is reduced to a minimum. The imperfect action of the 
valve gears may also be lessened with due care, but the action of 
the cylinder walls still remains to be overcome. 

Theoretical and Actual Card Analysis. In the theoretical card, 
admission is at constant boiler pressure, cut-off is sharp, expansion 
is complete — that is, expansion continues until the temperature falls 
to that of the condenser and the exhaust is at condenser pressure — 
and the piston always sweeps the full length of the cylinder. 

In the actual engine there is a considerable loss of pressure 
between boiler and engine, and the wire drawing of the ports and 
valves tends to cause a sloping steam line. Condensation at the 
beginning of the stroke causes the real expansion line to fall below 
the theoretical, while re-evaporation causes it to rise above the theo- 
retical toward the end of expansion. In the actual engine, release 
takes place before the end of the stroke, expansion is not complete, 
that is, the pressure at release is above that of the condenser, and the 
resistance of exhaust ports causes the back pressure to be above the 
actual condenser pressure. Moreover, the piston does not sweep the 



108 STEAM ENGINES 

full length of the cylinder, and the clearance space must be filled with 
steam, which does very little work. The theoretical and actual 
cards are shown in Fig. 71. 

Mechanical Losses. It has been shown that the efficiency of 
the theoretical engine is purely a thermal consideration; the efficiency 
of the actual engine, however, is largely a mechanical matter. The 
unit of work is the horsepower, which corresponds to the develop- 
ment of 33,000 foot pounds per minute. As 778 foot pounds are 
equivalent to one British Thermal Unit, 33,000 foot pounds per 
minute, or one horsepower, is equivalent to 33,000 -i- 778 or 42.42 
British Thermal Units. Now if a certain engine uses 84.84 British 




Fig. 71. Superposed Ideal and Actual Indicator Diagrams 

Thermal Units per horsepower per minute, it is evident that its 
efficiency will only be one-half, or 50 per cent, because 42.42 is one- 
half of 84.84. Hence, it may be said that the efficiency of the actual 

. • , . 42.42 

engine is equal to -—— . 

rSntisn lnermal units per horsepower per minute 

This efficiency is always much less than that of the perfect engine. 

ANALYSIS OF LOSSES 

The effect of some of the losses in the steam engine and the 
methods for decreasing them will now be considered. 

Radiation. In the first place, the metal walls of the cylinder, 
being good conductors of heat, become heated by the steam within 
and transmit this heat by conduction and radiation to the air or 
external bodies. With the cylinder well lagged, much less heat is 
lost by radiation. If the lagging were perfect and the temperature 



STEAM ENGINES 109 

of the cylinder remained the same as the temperature of the steam 
throughout the stroke, there would be no loss by radiation, but heat 
would still be lost by conduction to the different parts of the engine. 

Cooling by Expansion. During expansion, the temperature and 
pressure of the steam decrease as the volume increases, and the tem- 
perature at exhaust is much less than the temperature at admission. 
In the perfect engine, the working substance after exhaust is com- 
pressed to the temperature at admission, but in the actual engine 
much of this steam is lost and the compression of a part of it is 
incomplete, so that its temperature is less than the temperature at 
admission. 

Steam Condensation and Re=Evaporation. Consider an engine 
operating with admission at 100 pounds absolute and exhaust at 
18 pounds absolute. From steam tables the temperature at admis- 
sion is found to be 327.86°, and at exhaust 222.4°. The metal walls 
of the cylinder, being good conductors and radiators of heat, are 
cooled by the low temperature of exhaust, so that the entering steam 
in passing through ports and into a cylinder is subjected to a tem- 
perature of more than 100° cooler than the steam. This means that 
heat must flow from the steam to the metal until both are of the 
same temperature. This causes the steam to give up part of its 
latent heat, and as saturated steam can not lose any of its heat 
without condensation, the cylinder walls become covered with a film 
of moisture, usually spoken of as initial condensation. This conden- 
sation in simple unjacketed engines, working under fair conditions, 
may easily be 2C per cent or more of the entering steam. The mois- 
ture in the cylinder has, of course, the same temperature as the 
steam ; it has simply lost its heat of vaporization. 

Although metal is a good conductor of heat, it can not give up 
or absorb heat instantly; consequently during expansion, the tem- 
perature of the steam falls more rapidly than that of the cylinder. 
This allows heat to flow from the cylinder walls to the moisture on 
them. As fast as the steam expands so that the pressure in the cylin- 
der becomes less, this condensation will begin to evaporate. As the 
pressure falls it requires less and less heat to form steam and, there- 
fore, more and more of this moisture will be evaporated. At release 
the pressure drops suddenly, more heat at once flows from the cylinder 
walls, and re-evaporation continues throughout the exhaust. Prob- 



110 STEAM ENGINES 

ably all of the water remaining in the cylinder at release is now 
re-evaporated, blows out into the air of the condenser, and is lost 
as far as useful work is concerned. 

The steam that is first condensed in the cylinder does no work ; 
its heat is used to warm up the cylinder, and later, when it is re-evap- 
orated, it works only during a part of the expansion and at a reduced 
efficiency, because it is re-evaporated at a pressure and, consequently, 
at a temperature very much lower than that of admission. If the 
cut-off is short, perhaps 20 per cent of the steam condensed may be 
re-evaporated during expansion; if the cut-off is long, 10 per cent 
may be re-evaporated, the rest remaining in the cylinder at release, 
still in the form of moisture. Thus some of the entering steam passes 
through the cylinder as moisture until after cut-off, and still more 
passes entirely through without doing any work. 

Suppose an engine is using 30 pounds of steam per horsepower 
per hour and admission is at 100 pounds absolute. The latent heat 
of vaporization at this pressure is 884 British Thermal Units per 
pound. If the condensation amounts to 33 J per cent, then 10 pounds 
are condensed and there is lost 10 times 884, or 8,840 British Thermal 
Units per hour, or 147.3 per minute; and since 42.42 British Thermal 
Units represent 1 horsepower, there is lost by condensation 147.3 
divided by 42.42, or 3| horsepower (nearly). If the cut-off is short- 
ened, the condensation increases and may amount to 50 per cent. 
Of course, very much less steam is used at a short cut-off than with 
a long cut-off, and doubtless in many cases 50 per cent of the steam 
at short cut-off is not as great an absolute quantity as 30 per cent at 
a long cut-off. 

Exhaust Waste. In addition to the actual loss from condensa- 
tion in the cylinder, there is still another loss due to re-evaporation. 
Suppose, as before, that 10 pounds of steam are condensed in the 
cylinder, and that 20 per cent of this is re-evaporated during expan- 
sion. This will leave 8 pounds to be re-evaporated during exhaust. 
Suppose the exhaust is at 3 pounds above atmospheric pressure, or 
18 pounds absolute (about). Then the heat of vaporization is 963.1 
British Thermal Units per pound of steam, and it will require 8 times 
963.1, or 7704.8 British Thermal Units, to evaporate the 8 pounds. 
All of this heat is taken from the cylinder, leaving the engine much 
cooler than it would be were it not for this re-evaporation. This 



STEAM ENGINES 111 

gives some idea of the great amount of heat passing away at exhaust, 
which is known as the exhaust waste. 

Clearance. In all cylinders it is necessary to have a little space 
between the cylinder cover and the piston when at the end of the 
stroke. In vertical engines the space is greater at the bottom than 
at the top. The volume of this space, together with the volume of 
the steam ports, is called the clearance. It varies from 1 to about 
15 per cent, depending upon the type and speed of the engine — the 
higher the speed, the greater the clearance. This clearance space 
must be filled with steam before the piston receives full pressure ; and 
the volume of the clearance offers additional surface for condensation. 

Friction. Another important loss is that due to friction. It is 
well known that it takes considerable power to move an unloaded 
engine; if fitted with a plain, unbalanced slide valve, the power neces- 
sary to move the valve alone is considerable. The piston is made 
steam-tight by packing rings, and leakage around the piston rod is 
prevented by stuffing boxes. All these devices cause friction as 
well as wear at the joints. The amount of power wasted in friction 
varies greatly, depending upon the kind of valves, general work- 
manship, state of repair, and lubrication. 

OPERATION ECONOMIES 

The foregoing discussion has served to indicate that the larger 
part of the heat loss occurring in the steam engine is due to initial 
condensation, exhaust waste, and clearance, although the effect of 
the latter has been greatly reduced by improvement in design. 
Regarding the methods devised for reducing the amount of initial 
condensation, the high-speed engine has in a measure decreased this 
difficulty because of the very high piston speed employed. Since 
the piston speeds are high, the length of time the steam remains in 
the cylinder has been greatly lessened; hence the transference of 
heat is considerably reduced. The piston speed is limited, however, 
by the performance of the valve gear, it being well known that the 
most efficient valve gears are those employed on the low-speed 
engines. Increased piston speed also calls for more clearance space, 
hence the possible gain in economy from high piston speed is limited 
by the performance of the valve gear and the clearance required 
for the higher speeds. 



112 STEAM ENGINES 

The application of the idea of multiple expansion, or compound- 
ing, has materially reduced the losses both by lessening the amount 
of condensation and also by utilizing the re-evaporated steam and 
the steam that leaks by the piston, which in some cases may be con- 
siderable, and this important improvement will be discussed first. 
In addition, other means have been employed for the purpose of 
increasing the economic performance of the steam engine, as for 
instance, jacketing, superheating, and the use of condensers. 

MULTIPLE EXPANSION 

Two engines may be used together on the same shaft, partly 
expanding the steam in one of the cylinders and then passing it over 
to the other to finish the expansion. One advantage from this 
arrangement is that the parts can be made lighter. The high-pres- 
sure cylinder can be of much less diameter than would be possible 
if the entire expansion were to take place in one cylinder. This, of 
course, makes the pressure exerted on the piston rod much less, and 
the piston rod and connecting rod can thus be made much lighter. 
The low-pressure cylinder must be larger than it otherwise would 
be, but its parts need not be much heavier, because the pressure per 
square inch is always low. 

This arrangement gives not only the advantage of lighter parts, 
but a decided increase of economy over the single-cylinder type. 
If attention is given to the matter, a loss of economy would be 
expected, because the steam is exposed to a much larger surface 
through which to lose heat, but the gain comes from another source 
and is sufficient to entirely counterbalance the effect of a larger cyl- 
inder surface. 

Less Condensation. When very high pressure steam and a large 
ratio of expansion is used, the difference between the temperature 
of the entering and of the exhaust steam is great. For instance, 
suppose steam at 160 pounds (gauge) pressure enters the cylinders 
and the exhaust pressure is 2 pounds (gauge), the difference in tem- 
perature as taken from steam tables is 370.7° — 218.2°, or 152.5°. 
This difference becomes nearly 230 degrees if the steam is condensed 
to about three pounds absolute pressure. The cylinder and ports of 
the engine are cooled to the low temperature of the exhaust steam 
and, as we have seen, a considerable quantity of the entering steam 



STEAM ENGINES 113 

is condensed to give up heat enough to raise the temperature of the 
cylinder to that of the entering steam. As the ratio of expansion 
increases, the difference in temperature increases, and consequently 
the amount of steam thus condensed also increases. To keep this 
initial condensation as small as possible, the range of temperature 
must be limited, that is, it must not have as great a difference between 
admission and exhaust. To do this the expansion of the steam 
must be divided between two or more cylinders. 

It will be remembered that the great trouble Watt found with 
Newcomen's engine was its great amount of condensation, and he 
stated as the law which all engines should try to approach, that the 
cylinder should be kept as hot as the steam which enters it. This is to 
avoid condensation when steam first enters. If, instead of expand- 
ing the steam in one cylinder, it be expanded partly in one and then 
finished in another, it will have passed out of the first cylinder before 
its temperature has dropped a great deal, and consequently the 
cylinder walls will be hotter than they would have been if the expan- 
sion had taken place entirely in one cylinder. This would then 
reduce the amount of steam condensed. The importance of this 
may not be evident at first, but it makes a great difference in the 
economy of the engine. If there is less condensation, there will be 
less moisture to re-evaporate, and consequently less exhaust waste, 
hence there will be a saving in two ways. 

Methods of Compounding. In a compound engine the steam 
is first admitted to the smaller, or high-pressure, cylinder and then 
exhausted into the larger, or low-pressure, cylinder. 

Suppose steam at 160 pounds (gauge) pressure is admitted to a 
cylinder, and the ratio of expansion is such that the steam is exhausted 
at about 60 pounds (gauge) pressure; then the difference of tempera- 
ture is 370.7° -307.4°, or 63.3°. 

If now the steam when exhausted from the first cylinder enters 
a second and is allowed to complete its expansion, so that the exhaust 
pressure is about two pounds (gauge) pressure, the difference of 
temperature in the cylinder will be 307.4° -218.2°, or 89.2°. 

Then for the simple engine, if the exhaust pressure is two pounds 
(gauge), the difference of temperature is 152.5 degrees, while in the 
compound engine this difference is divided into two parts, 63.3 
degrees and 89.2 degrees. The cylinder condensation for both 



114 STEAM ENGINES 

cylinders of the compound engine will be much less than if the total 
expansion took place in a single cylinder. The cylinders should be 
so proportioned that the same quantity of work may be done in each. 

If there are two stages of expansion, the engine is called simply 
compound; three stages, triple; and four, quadruple. 

Exhaust Waste Utilized. Besides reducing the excessive conden- 
sation, there is still another gain in using multiple expansion. It has 
been shown how much heat is lost by the exhaust waste, which in 
the simple engine blows into the air or into the condenser and is 
entirely lost. In the multiple-expansion engine the exhaust and 
re-evaporation from one cylinder passes into the next and does work 
there; furthermore, any leakage from the high-pressure cylinder is 
also allowed to do work in the low-pressure cylinder. 

JACKETING 

The most primitive method of effecting steam economy is by 
jacketing, which principle Watt early recognized and adopted. This 
method reduces the loss due to cylinder condensation by supplying 
heat to the steam while it is in the cylinder, that is, by surrounding 
the cylinder with an iron casting and allowing live steam to circulate 
in the annular space thus formed. The cylinder covers are also 
made hollow to permit a circulation of live steam. A cylinder having 
the annular space A, Fig. 72, filled with steam is said to be jacketed. 
A lining L is often used in jacketed cylinders. 

Function of Jacket. The function of the jacket is to supply 
heat to the cylinder walls to make up for that abstracted during 
expansion and exhaust, so that at admission the cylinder will be as 
hot as possible. The result is, that the difference in temperature 
between the cylinder walls and the entering steam is considerably 
less than in engines where no jacket is used. Condensation is there- 
fore reduced and, since heat flows from the jacket to the cylinder 
during expansion, a much larger amount of this condensation is 
re-evaporated before release and it thus has an opportunity to do 
some work in the cylinder. This leaves a comparatively small 
amount of exhaust waste and the heat thus abstracted is made up 
from the steam in the jacket. Since a large amount of heat is given 
up by the jacket steam, a good deal of it must be condensed. Thus 
the question is asked: "What is the advantage of this method over 



STEAM ENGINES 



115 



that of allowing the entering steam to supply the heat by its own con- 
densation?" This question is answered briefly as follows: 

The loss of heat by condensing the steam would be less if the 
inside of the cylinder could be kept dry. It has been indicated how 
the moisture that collects by condensation is re-evaporated during 
expansion and exhaust because the pressure falls and the cylinder 
walls are hotter than the steam. This re-evaporation takes place at 
the expense of the heat in the cylinder walls and they are thus cooled. 
It has already been shown that a great many British Thermal Units 




Fig. 72. Section of Steam Engine Cylinder, Showing Method of Jacketing 



are thus taken from the cylinder and thrown out at exhaust at every 
stroke. Now if the inside of the cylinder can be kept dry so that 
there will be little or no re-evaporation at exhaust, it will cause a 
ponsiderable saving. The steam that condenses in the jacket does 
aot re-evaporate in it; but is returned to the boiler as feed water, 
io that the only heat lost is the latent heat given up during conden- 
sation. If the cylinder is heated from within, both the latent heat 
given up by condensation and the latent heat required for re-evapora- 
tion are lost. 

In a triple-expansion engine there is one distinct advantage in 
allowing condensation in the cylinder, for this moisture acts as a 
lubricant, and as the heat of re-evaporation passes into the next 
cylinder and there does work, there is very little loss. 



116 STEAM ENGINES 

Saving Due to Jacketing. It is evident that a large part of the 
heat of the steam jacket flows to the cylinder during exhaust and is 
thus entirely lost in the simple engine. In the triple engine, how- 
ever, this heat passes into the intermediate and low-pressure cylin- 
ders; consequently we might expect a greater gain from using a 
jacket on a triple engine than on a large, simple engine. The main 
advantage of the jacket has been previously pointed out, and as 
in all cases the gain is small, there is to be found a considerable 
diversity of opinion as to its real advantages. On some engines 
there is undoubtedly little if any gain, the largest gain being in the 
smaller engines of, say, 200 horsepower and under. On very small 
engines, such as a 5-inch X 10-inch engine when developing only one 
and one-half horsepower under light load, the gain is as much as 
30 per cent. On a 10-horsepower engine the gain might be as 
much as 25 per cent, while on engines of about 200 horsepower the 
gain would probably be 5 to 10 per cent for simple condensing 
and compound condensing, and from 10 to 15 per cent for triple 
expansion. The saving on large engines of, say, 1,000 horsepower 
is very small, the reason being that large engines offer less cylinder 
surface per unit of volume than small ones, and hence have propor- 
tionately less cylinder condensation. The very small engines, in 
which the gain would be the greatest, are seldom jacketed, because 
they are built for inexpensive machines and the first cost is of more 
consequence than the economy of operation. Owing to the cost of 
construction and the care necessary to keep jackets operative, the 
use of the jacket has gradually diminished. Furthermore, the intro- 
duction of the high-speed and compound engines, as well as the use 
of superheated steam, has reduced the advantage of jacketing to 
relative insignificance. 

SUPERHEATING 

General Practice. The use of superheated steam is rather a 
modern practice, although for many years previous to its adoption 
engineers had appreciated its value in producing steam engine econ- 
omy. The reason for its delayed adoption in a practical way was 
due to the mechanical difficulties met with in superheating the 
steam and also to the increased cost of maintenance produced by 
its use. In recent years both of the objectionable features above 
mentioned have been, in a large measure, overcome, so that today 



STEAM ENGINES 



117 



superheat is being used in a large number of power plants, and also 
in steam locomotives. 

Before describing a superheater, it may perhaps be well to 
clearly define what is meant by superheated steam. Water, when 
confined in a vessel and heated sufficiently, turns into steam, which, 
if some water still remains, is spoken of as saturated steam. Satur- 
ated steam when further heated becomes superheated steam, if it 
is separated from the water. To bring about this separation, a 
superheater is necessary. Superheaters vary considerably in details 
of construction according to the service for which they are designed, 




Fig. 73. Section of Water-Tube Boiler Showing Application of Foster Superheater 

there being, for instance, quite a difference between the superheater 
designed for a stationary plant and one designed for a locomotive. 

Foster Superheater. A Foster superheater as applied to a water- 
tube boiler is illustrated in Fig. 73. The superheating element 
is shown at B, which is connected to the steam space of the boiler by 
the pipe A. The saturated steam from the boiler passes through 
the pipe A, through the superheater, and then is conveyed to the 
engine through the valve C. In this installation the superheater is 
placed in the passage provided for the transmission gases to the 
chimney, hence it is heated by what would otherwise be lost heat. 
The manner of installing superheaters varies a great deal. Some are 



118 



STEAM ENGINES 



entirely separated from the boiler, being self-contained and supplied 
with a grate for separate firing. 

The Foster superheater, Figs. 73 and 74, is made up of a num- 
ber of elements placed parallel to each other, each of which consists 
of two straight steel tubes, one inside of the other. The elements 
are joined at one end to manifolds or connecting headers, and at the 
other end to return headers for which return bends are often substi- 
tuted. On the outside of the tubes B, Fig. 74, are fitted a series of 
cast-iron annular flanges D, placed close to each other and carefully 
fitted to the tube so as to be practically integral with it, at the same 
time exposing an external surface of cast iron, which metal is best 
adapted to resist the action of the heated gases. The rings are care- 
fully bored to gauge, and shrunk on the tubes. Once being in posi- 
tion, the rings and tubes act vir- 
tually as a unit. As the coeffi- 
cient of expansion of steel is a trifle 
greater than that of cast iron, the 
rings grip the tubes even tighter 
when in service. This form of 
construction is flexible and dur- 
able. It provides a section of 
great strength and entire freedom 
from internal strains. The mass 
of metal in the tubes and covering 
acts as a reservoir for heat, which 
is imparted to the steam evenly, 
tending to secure a constant tem- 
perature of steam, even though the temperature of the hot gases does 
fluctuate. The seamless drawn tube secures great initial strength, 
which is reinforced by the rings shrunk on the outside. Inside of 
the elements there are placed other tubes C of wrought iron, which 
are centrally supported by means of knobs or buttons regularly 
spaced throughout their length. These inner tubes are closed at the 
ends. A thin annular passage E from the steam is thus formed 
between the inner and the outer tubes. The steam clinging closely 
to the heating surface is quickly heated in the most efficient manner. 
The superheater must be as free as possible from the liability 
of burning out in case of a chance of overheating of the exposed 




Section of Foster Superheater Tubes 



STEAM ENGINES 



119 



surfaces. The circulation must be properly distributed throughout 
the superheater at full load as well as at partial loads. The various 
parts must be accessible for inspection, both externally and inter- 
nally, and must be readily renewable or easily repaired. There must 
be provision for free expansion and contraction of the various parts. 
The supporting arrangement must be carefully worked out. Cast 
iron has given excellent results in producing durable superheaters 



SECT/ON A-B 




Fig. 75. Section of a Separately-Fired Type of Superheater 

and has been extensively used because of its ability to withstand high 
temperatures. For high steam pressures, however, cast iron is not 
considered safe and has given way to the use of seamless steel tubes, 
which are homogeneous and strong, but lack the heat-resisting quali- 
ties of cast iron. It is evident that a combination of these two 
metals will preserve the good qualities of both. 

Separately=Fired Superheater. A type of superheater differ- 
ing radically from the one previously described is illustrated in Fig. 
75. It is a separately-fired superheater and its construction is very 



120 STEAM ENGINES 

similar to the Stirling water-tube boiler. The saturated steam from 
the main boiler plant enters the rear superheater drum 1, passe- 
through the rear bank of tubes 7 into the lower drum 2, thence to the 
upper drum 3, from which it passes into the pipe line through the 
opening 4- The furnace is similar to that used in the standard 
design of Stirling boiler. To protect the superheater tubes from 
high temperatures of the furnace, a sufficient amount of boiler heat- 
ing surface, as drums 5 and 6 and bank of tubes 9, is located in front 
of the superheater proper in order to reduce the temperature of the 
gases to about 1,500 degrees by the time they reach the superheater. 
The builders state that when the gas temperature reaches 1,500 
degrees in the standard boiler, 19 per cent of the boiler heating sur- 
face has been swept over by the gases, 50 per cent of the steam pro- 
duced by the boiler has been generated, and the boiler heating surface 
per horsepower is 3.8 square feet. Consequently in the independently 
fired superheater shown in Fig. 75, 50 per cent of the heat absorbed 
is used to generate the steam, which is added to steam furnished by 
the main boiler plant and hence increases the capacity of the plant in 
proportion. The remaining 50 per cent of the heat, a portion of 
which passes out the stack, is absorbed by the superheater and super- 
heats both the steam from the main boiler plant and that from the 
front bank of water tubes. The superheater, because of the front 
generator set, will produce about 12 per cent of the amount of 
steam furnished by the main boiler plant. As a further precaution 
against any possible overheating of the superheater tubes near the 
furnace, a flap valve 12 is placed in the pipe conveying saturated 
steam to the superheater, as shown in Fig. 75. The spindle of thLs 
valve is connected by links to the superheater damper 13, so that 
the damper to the opening is regulated according to the quantity 
of steam flowing into the superheater. If the steam flow stops, the 
valve 12 drops to its seat and the damper 13 is closed. Independ- 
ently fired superheaters are furnished in any desired capacity, suit- 
able for any degree of superheat up to about 300° F. The upper 
water drum 5 and the lower superheater drum 2 are connected by 
piping, hence, if desired, the superheater sections may be flooded, 
converting the whole into a saturated steam boiler. 

Purposes of Superheaters. These two types of superheaters 
illustrated and described will suffice, and we may now direct our 



STEAM ENGINES 121 

attention to a study of the purposes of the superheater and to 
some consideration of the economy secured by its use. The pur- 
poses of superheating steam, as practiced in the past and as recog- 
nized at present, are, according to Thurston, the following: 

(1) Raising the temperature which constitutes the upper limit 
in the operation of the heat-engine in such a manner as to increase 
the thermodynamic efficiency of the working fluid. 

(2) To so surcharge the steam with heat that it may surrender 
as much as may be required to prevent initial condensation at 
entrance into cylinder and still perforin the work of expansion with- 
out condensation or serious cooling of the surrounding walls of the 
cylinder. 

(3) To make the weight of the steam entering the condenser 
and its final heat charge a minimum, with a view to the reduction 
of the volume of the condensing water and of the magnitude and cost 
of the air pump and condenser system to a minimum. 

(4) To reduce the back pressure and thus to increase the power 
developed from a given charge of steam and efficiency of the engine. 

(5) To increase the efficiency of the boilers both by the reduc- 
tion of the quantity of the steam demanded from the original heat- 
ing surface and by increasing the area of the heating surface employed 
to absorb the heat of the furnace and flue gases, and also by evading 
the waste consequent upon the production of wet steam. 

If the steam entering a cylinder is only superheated enough to 

Ti-T 2 

give dry saturated steam at cut-off, the range of temperature — jp, — 

of the Carnot cycle is interchanged and there is, therefore, no increase 
of economy from item 1. The other four sources of economy depend 
upon one fundamental fact — the poor conductivity of dry steam. 
To the property of non-conductivity of heat of superheated steam 
is due its great advantage. On entering a cool cylinder it slowly 
gives up its heat, and if the degree of superheat is sufficient there will 
be little or no initial condensation. The degree to which steam 
should be superheated is still a debated point, some engineers con- 
tending that only a very moderate degree of superheat of about 100 
degrees is sufficient, whereas others maintain that no real economy is 
obtained with less than 200 degrees or over. When a high degree 
of superheat was first used, difficulties were encountered such as 



122 STEAM ENGINES 

the disintegration of the valves, valve seats, packing rings, and other 
parts subjected to the action of the superheated steam. Lubrication 
was also interfered with, since many of the oils used were not suited 
for such high temperatures. All of these difficulties no doubt account 
for the one time widespread objection to high degrees of superheat, 
but in recent years they have in a large measure been overcome. 
The author is familiar with the performance of a simple slide valve 
locomotive which has been in operation for several years under degrees 
of superheat ranging from 80 degrees to 214 degrees, during which 
time no trouble has been experienced with the valves or with the 
lubrication. Many European locomotives have been satisfactorily 
operated with high degrees of superheat, which insures the passage 
of steam through the cylinder with but little or no condensation. 

Economic Advantages. The economy obtained by the use of 
superheat has been clearly demonstrated by a large number of prac- 
tical tests both upon stationary engines and upon locomotives. It is 
to be noted also, that about the same per cent of economy has been 
obtained on the various types of engines tested, the stationary tests 
corroborating the results obtained upon the locomotive and vice 
versa. The various tests indicate a saving of from 12 to 15 per cent 
of the amount of steam used by the engine per indicated horsepower 
per hour, and a saving of coal from 20 to 25 per cent. Another very 
significant thing that has been determined is that the output of 
power has been increased from 20 to 30 per cent, depending upon 
the conditions. These three items of saving have hastened the 
installment of a large number of superheaters, so that at the present 
time thousands of locomotives in Europe are equipped with super- 
heaters, and in the United States and Canada over 1,500 locomo- 
tives are so equipped. It seems that the railroads have been 
quicker to take up the idea of installing superheaters than have other 
industries, so that not nearly so many superheaters are found in 
stationary service. 

It is to be noted that the greatest gains from the use of super- 
heaters are to be expected in the more uneconomical plants. That is, 
the per cent of saving by the use of superheated steam in a simple 
engine would be greater than for a compound engine, and for a com- 
pound engine as compared with a triple-expansion engine. Several 
prominent engineers have advised the reduction of steam pressures 



STEAM ENGINES 123 

with a relative increase in diameter of cylinders and the use of super- 
heated steam. The combination of a simple engine with low steam 
pressure and superheated steam will give an increased output of 
power at a small cost, a result desired by all operators. 

CONDENSERS 

When low-pressure steam is cooled, it gives up its latent heat, 
that is, it changes from a vapor to a liquid, and, as a liquid occupies 
much less space than an equal weight of its vapor, the changing of 
the steam to water greatly reduces the pressure. Therefore, by 
cooling the steam in an engine cylinder in front of the piston, the 
back pressure, or resistance, is reduced, which, in turn, reduces the 
pressure necessary to push the piston through the stroke and, there- 
fore, lessens the steam required to do the work. This cooling is 
accomplished by some form of condenser. 

Theory of Condenser Action. Back Pressure. In the ordinary 
non-condensing engine, steam can not be exhausted below a pressure 
of 14.7 pounds absolute, because the atmosphere exerts that amount 
of pressure at the opening of the exhaust pipe. In fact, this 14.7 
pounds is the theoretical limit only, and in practice the exhaust is 
always a little above this because of resistance in the exhaust ports 
and exhaust pipe; so that 17 or even 18 pounds absolute back pres- 
sure is more nearly the conditions of actual service. 

During the forward stroke, steam expands from the pressure 
at admission to a much lower pressure at release; then the valve opens 
for the return stroke giving full steam pressure on one side of the 
piston and the pressure of exhaust on the other side, the latter act- 
ing against the piston and against the force of the incoming steam. 
If all of this back pressure could be removed so that there would be 
a vacuum on the exhaust side of the piston, the power of the engine 
would be increased by just so many pounds of mean effective pres- 
sure, and in addition to this the steam could expand to a very much 
lower pressure and therefore work with greater economy. 

Effect of Condensation. One pound of steam at 17 pounds 
absolute pressure occupies 23.38 cubic feet of space in the cylinder 
of the engine, but one pound of water in the condenser occupies only 
about 0.016 cubic feet, which makes the steam occupy nearly 1,462 
times as much space as the water into which it condenses. If then, 



124 



STEAM ENGINES 



the exhaust steam could be condensed instantly, the back pressure 
would be reduced almost to zero and the engine would exhaust into 
a vacuum. 

Unfortunately the mere condensation of the steam will not give 
a perfect vacuum because of the air, always present in the water 
which comes over from the boiler. Moreover, the condensed water 
is hot, and the vapor rising from it in the condensing chamber, 
together with the air and some leakage would spoil the vacuum were 



EXf/Al/ST ///LET 



WATER OUTLET 




Fig. 76. Section of Steam Condenser of the Surface Type 

it not for the air pump, which removes the air and condensed steam. 
Even with the best air pump it would be impossible to maintain a 
perfect vacuum, but a vacuum of 26 inches, which corresponds to 
about 2 pounds absolute pressure, can readily be maintained in 
good practice. 

It is well known that a certain amount of heat is required to 
change one pound of water at a given temperature into steam at 
the same temperature; this is called the latent heat of vaporization. 
If the steam condenses, it must give up this latent heat. The easiest 
ways of doing this are either to let the steam come in contact with 



w 



STEAM ENGINES 



125 



pipes through which cold water is circulated, as in a surface condenser, 
or mingle with a spray of water, as in a jet condenser. These two 
types will now be discussed. 

Types of Condensers. Condensers may be divided into two 
general classes as follows: 

(1) Surface condensers in which the cooling water is separated 
from the steam, usually by metallic surfaces in the form of tubes, 
the cooling water circulating on one side of this surface and the steam 
coming in contact with the metal on the other side. 

(2) Jet condensers, including barometric condensers, siphon 




Fig. 77. Diagram Showing Relation of Surface Condenser to the Pumps Necessary for 

Proper Operation 

condensers, ejector condensers, etc., in which the cooling water 
mingles with the steam to be condensed. 

Surface Type. The condenser shown in section in Fig. 76 is one 
form of the surface type, in wmich the air pump and the circulating 
pump are both direct acting and both operated by the same steam 
cylinder. The cool condensing water is drawn from the supply into 
the circulating or water pump and is forced up through the valves 
and water inlet to the condenser. It flows, as indicated by the 
arrows, through the inner tubes of the lower section, then back 
through the space between the inner and the outer tubes. The 
water then passes upward and through the upper section, as it did 
in the lower, then it passes out of the condenser through the water 
outlet, taking with it the heat it has received from the steam. 



126 STEAM ENGINES 

The exhaust steam from the engine enters at the exhaust inlet 
and comes in contact with the perforated plate, which causes it to 
spread. The steam expanding in the condenser comes in contact 
with the tubes, through which cool water is circulating, and con- 
denses. The air pump draws the air and condensed steam out of 
the condenser and thus maintains a partial vacuum. This causes 
the exhaust steam in the engine cylinder to be drawn into the con- 
denser, at the bottom of which it collects as it condenses and is 
drawn into the air pump cylinder and discharged while heated to 
the hot well of the boiler. The use of this hot water as feed water 
effects a considerable saving, but the great advantage of the con- 
denser is the reduction of the back pressure. 

Hot water can not be used by an ordinary pump as easily as 
cold water because of the pressure of the vapor which arises from 
the hot water. In the condenser shown, the water and air pumps 
are run by the piston in the steam cylinder. Sometimes these pumps 
are connected to the main engine and receive motion from the shaft 
or crosshead. 

The general arrangement of the surface condenser with the 
necessary pumps is shown in Fig. 77. The cooling water enters 
through the pipe K and flows to the circulating pump R, which 
forces the water into the condenser through the pipe L. In case 
the water enters the condenser under pressure from city mains, no 
circulating pump is necessary. After flowing through the tubes it 
leaves the condenser by means of the exit M and flows away. Exhaust 
steam enters at S and is condensed by coming in contact with the 
cold tubes; the water (condensed steam) then falls to the bottom of 
the condenser \ nd flows to the air pump B by the pipe E. The air 
pump removes the air, vapor, and condensed steam from the con- 
denser and forces it through the pipe N into the hot well, from which 
it goes to the boilers or to the feed tank. 

Circulating Pump. The circulating pump, when separate from 
the condenser, is usually of the centrifugal type. This pump con- 
sists of a fan or wheel which is made up of a central web (or hub) and 
arms (or vanes). The vanes are curved and as the water is drawn 
in at the central part, the vanes throw it off at the circumference. 
A suitable casing directs the flow. This type of pump is advanta- 
geous because there are no valves to get out of order and, as the lift 



STEAM ENGINES 



127 



is little, if any, the pump will discharge a large volume of water in a 
nearly constant stream. The circulating pump is usually so placed 
that the water flows to it under a slight head. The pump is driven 
by an independent engine so that the circulating water may cool 
the condenser even if the main engine is not working. 

Jet Type. Fig. 78 illustrates the longitudinal section of an 
independent jet condenser and pump. The cold water used to con- 
dense the steam enters at A, passes down the spray pipe B, and is 
broken into a fine spray by means of the spray cone C. This action 
insures a rapid and thorough mixing of the steam and water and 
consequently a rapid condensation. The 
exhaust steam enters at D with a compara- 
tively high velocity, which is imparted to 
the water. The whole mixture of water, 
steam, and vapor passes at high velocity 
through the conical chamber E to the pump 
cylinder F, where it is forced into the pipe 
G. The spray cone is adjusted by means of 
the stem which passes through the stuffing 
box at the top of the condenser. The 
valves are shown at // and K. The steam 
end of the pump is at L. 

In Fig. 79 a jet condenser is shown con- 
nected to a stationary engine. The exhaust 
pipe leads from the engine to the condenser, 




Fig. 78. Longitudinal Section of Independent Jet Condenser and Pump 



■WATER DISTRIBUTING 
TRAY 



AIR PUMP SUCTION 



Egff: 




Fig. 80. Alberger Barometric Jet Condenser 
Courtesy of Alberger Pump and Condenser Company, New York City 



130 STEAM ENGINES 

the arrows indicating the direction of the flow. Cold water enters 
the condenser through the pipe shown. Part of the mixture of 
exhaust steam and condensed water goes to the feed- water heater, 
which is kept nearly full; the rest passes to the sewer. The heater 
is placed a little above the feed pump, in order that the water may 
enter the pump under a slight head. This is necessary because the 
pump can not raise water which has been warmed by exhaust steam 
as readily as cold water. 

Barometric Condenser. A type of condenser much used with 
reciprocating engines, and to a limited extent with steam turbines, 
is the barometric condenser, shown in Fig. 80. This condenser is 
one of the jet type. Steam enters at the point marked "exhaust 
inlet" in the left-hand figure and completely fills the exhaust steam 
chamber, while the condensing water enters through the injection 
pipe. The water rises into a distributing tray where it is broken 
up into many finely divided streams as seen in the left-hand 
figure. This spray condenses the steam in the exhaust chamber 
and passes down the tail pipe, carrying the condensed steam with 
it to the hot well. Air entering with the exhaust steam is cooled 
and collected in the air collector inside of the condensing cham- 
ber. A vacuum is maintained in the upper part of the condenser 
so that any air which has been collected during the process of con- 
densing the steam is carried away through the pipe marked "air 
pump suction". A small amount of the cooler injection water is 
allowed to mix with this air so as to cool it before it passes on to 
the air pumps. 

Westinghouse Leblanc Condenser. With the ordinary type of 
reciprocating engine, a vacuum of 26 to 27 inches is usually all 
that is desired. With modern steam turbines, however, a vacuum 
of 28 to 29 inches is common practice, and in many plants even 
these figures are exceeded. These figures, however, cannot be 
attained unless a very efficient air pump is used. The Leblanc 
condenser is considered one of the most efficient types of the many 
forms of jet condensers. 

Fig. 81 shows a cross section of the Leblanc jet condenser, as 
manufactured by the Westinghouse Machine Company. This type 
is especially used in the larger steam turbine installations. In this 
condenser steam enters through the large opening E at the top, 



STEAM ENGINES 



131 



and the cooling water through B. This water is carried all around 
the circumference of the top of the condenser by the annular chamber 
C and is drawn inside the cone P through helical spray nozzles 1), 
by the vacuum in the condenser. Inside of the cone P the water 










Fig. 81. Cross Section of Leblanc Jet Condenser 
Courtesy of Westinyhouse Machine Company, East Pittsburgh, Pennsylvani 



is intimately mixed with the steam, condenses it, and falls to the 
bottom of the condenser. From here the water pumps F discharge 
the water from the condenser. The air released in the condenser 
by the water and condensed steam rises underneath the cone P, and 
is drawn off through the pipe L by the air pump A A. The inlet 



132 



STEAM ENGINES 



/ is the separate water supply for this air pump, shown more in 
detail by Fig. 82, which is a cross section on A A. 

In Fig. 82, the water entering through the center of the pump 
is discharged through the orifice J into a tapering pipe, the water 
being emitted in a succession of layers, as indicated at G. These 
layers of water are sometimes spoken of as being water pistons. 
The air coming through pipe L is caught between these layers of 
water and carried to the atmosphere through the long diffuser 
pipe K. 



en 



■p 



^""SYiV; 



S 'i»''"^ w " -.u-.u, ^ 



/r 



„ 




Section J7/7 



Fig. 82. Section of Leblanc Condenser Taken through AA, Fig. 81 
Courtesy of Westinghouse Machine Company, East Pittsburgh, Pennsylvania 



Since the cooling water enters by virtue of the vacuum, an 
accidental stopping of the pumps might cause serious trouble, due 
to the water rising above the top of the condenser. To take care 
of such emergencies, a very simple form of vacuum breaker is pro- 
vided. In case the water rises in the condenser to an undesirable 
height, the float 0, Fig. 81, opens the valve N and admits air to 
enter through passage Q directly into the condensing zone. This 
immediately stops the inflow of water by breaking the vacuum, 
r and prevents damage to the turbine. 

Relative Merits of Jet and Surface Condensers. In the jet con- 
denser the steam, as soon as condensed, becomes mixed with the 
cooling water, and if the latter should be unsuitable for boiler-feed 
because of scale-forming impurities, acids, salts, etc., the pure dis- 
tilled water represented by the condensed steam is wasted, and if it 
were necessary to purchase other water for boiler-feeding, this might 
represent a considerable waste of money. On the other hand, if the 



STEAM ENGINES 133 

cooling water is suitable for boiler-feeding or if a fresh supply of good 
water is easily obtainable, the jet condenser, because of its simplicity 
and low cost, is unexcelled. Surface condensers are recommended 
where the cooling water is unfitted for boiler-feed and where no 
suitable and cheap supply of pure boiler-feed water is available. 
Condensed steam from a surface condenser makes the best boiler- 
feed water, being in fact pure distilled water entirely free from scale- 
forming matter and containing a considerable amount of heat, as 
compared with cold feed water. If the exhaust from reciprocating 
engines is to be condensed and used as boiler-feed water, a suitable 
oil separator should be interposed in the exhaust pipe between the 
engine and the condenser. Another advantage of the surface con- 
denser as compared with the jet condenser is that there is no dan- 
ger, in case of failure of vacuum pumps, of the circulating water 
backing up into the engine cylinder and wrecking the engine. 

Effect of Condenser on Efficiency. It has already been stated 
that there is a gain in thermal efficiency by running an engine con- 
densing, but it will be more clearly seen by considering a few figures. 
The thermal efficiency may be expressed by the previously men- 
tioned formula 



E = 



T, 



This efficiency may be increased if 7\ can be made larger — 
which would happen if the boiler pressure were increased — or if 
T 2 can be made smaller, which would result from reducing the back 
pressure by condensing. If the boiler pressure is raised, both the 
numerator and denominator of the fraction will increase, and the value 
of the fraction will be but slightly greater. If, however, the back 
pressure is reduced, the numerator 7\— T 2 will be larger, while 
the denominator 7\ will remain the same. It is apparent that this 
will cause a much greater increase in efficiency than raising the 
boiler pressure a like amount. 

Suppose an engine is supplied with steam at 85.3 pounds (gauge) 
pressure and it exhausts at 3.3 pounds (gauge) pressure. The abso- 
lute temperature corresponding to 85.3+14.7, or 100 pounds pres- 
sure, is 327.86+459.5, or 787.36 degrees, and the absolute temperature 
corresponding to 3.3 + 14.7, or 18 pounds pressure, is 222.40+459.5, or 



134 STEAM ENGINES 

TABLE I 
Increase in Efficiency by Use of Condenser for Various Engines 



Type of Engine 


Feed Water per Indicated Horsepower 


Per Cent 
Gained 

„ b y 

Condenser 


Non-Condensing 


Condensing 


Probable 
Limits 
Pounds 


Assumed 
for Com- 
parison 
Pounds 


Probable 
Limits 
Pounds 


Assumed 
for Com- 
parison 
Pounds 


Simple High Speed 
Simple Low Speed 
Compound High Speed 
Compound Low Speed 
Triple Exp. High Speed 
Triple Exp. Low Speed 


35 to 26 
32 to 24 
30 to 22 

27 to 21 


33 
29 
26 
24 
24 


25 to 19 
24 to 18 
24 to 16 
20 to 12| 
23 to 14 
18 to 12 


22 

20 

20 

18 
17 


33 
31 
23 
25 

29 



681.9 degrees. Then the thermal efficiency determined from the 
formula becomes 

F= T 1 -T 2 787.36-681.9 
r l\ ~ 787.36 
= .134, or 13.4 per cent 

If the boiler pressure were raised to 140 pounds absolute, the 
efficiency would be 

812.59-681.9 
812.59 
= .161, or 16.1 per cent 

If instead of increasing the boiler pressure a condenser is used 
and the exhaust pressure reduced to 4 pounds (absolute), the effi- 
ciency becomes 

^- 787 - 3 7 6 8 - 3 6 f- 5 = .222, or 22.2 per cent 

Thus it is seen that if the exhaust pressure is lowered 14 pounds 
absolute there will be a greater increase in efficiency than if the 
boiler pressure is raised 40 pounds. 

The per cent of efficiency that is obtained by the use of a con- 
denser is shown in Table I. 

Cost of Cooling Water Determines Condenser Economy. While 
the above figures are very encouraging, yet conditions may arise 
where the per cent of gain may be materially lessened or entirely lost, 



STEAM ENGINES 135 

due to the cost of water. Condensing engines require from 20 to 
30 pounds of cooling water to condense each pound of steam used, 
depending on the necessary temperature. Thus it can be seen that 
the quantity of cooling water is relatively very large, and if it is 
purchased from a water company, quite an item is added to the 
yearly expense account for the one item of water. If, however, 
some means could be provided whereby the circulating water as it 
issues from the condenser could be cooled and then used over again 
in the condenser, the non-condensing engine could be run condens- 
ing, thus taking advantage of all the benefits due to the use of reduced 
back pressure and heating of the feed water. This has been 
attempted by conducting the heated discharge water to a pond, 
where it is allowed to cool to a lower temperature before being used 
again. Another plan is to place in the yard or on the roof of the 
building large shallow pans, in which the water is cooled by being 
exposed to the atmosohere. These methods are unsatisfactory on 
account of the considerable area necessary and the slow action. In 
addition, they are uncertain, because they are dependent upon 
atmospheric conditions. 

Cooling Toicer and Water Table. A more efficient and at the 
same time more expensive process is to use a cooling tower or a 
water table. Fig. 83 illustrates the general arrangement of a cool- 
ing tower located upon the roof of a building. The discharge from 
the condenser is led, as shown by the arrows, to the top of the cool- 
ing tower, where it is cooled before being returned to the condenser. 
This cooling is effected by distributing the water, by a system of 
piping, to the upper edge of a series of mats or slats, over the surface 
of which the water flows in a thin film to a reservoir which is situated 
in the bottom of the cooling tower. The mats partially interrupt 
the flow and, by breaking up the water in small streams, cause new 
portions to be exposed to the cooling effect of the air currents. The 
water from the reservoir then flows downward through the suction 
pipe and is pumped by the circulating pump through the condenser. 
After passing through the condenser and absorbing heat from the 
exhaust steam, it rises through the discharge pipe and commences 
the circuit over again. 

The tower may have several arrangements and be made of vari- 
ous materials. A satisfactory form is constructed of steel plates 



136 



STEAM ENGINES 



within the tower, or a large number of mats of steel wire cloth gal- 
vanized after weaving. The tower may be supported upon a proper 
foundation or upon legs, instead of being situated on the top of a 
building, as the one shown in the illustration. 

To assist in the cooling of the water, the air is often made to 
circulate rapidly by means of a fan, which forces the air into the 




Fig. 83. Diagram of Stationary Engine with Connections to Water Cooling Tower on 

Roof of Building 

lower part of the tower and upward through the mats. This fan 
may be driven by an electric motor, by a line of shafting, or by a 
small independent engine. 

In case the fan is not used, the mats are arranged so that they 
are exposed to the atmosphere. This of course necessitates the 
removal of the steel casing. Usually the fanless tower must be 



STEAM ENGINES 137 

placed at the top of a high building or in some position where the 
currents of air can readily circulate through the mats. 

With an efficient type of cooling tower, the water may be reduced 
from 30 to 50 degrees, thus allowing a vacuum of from 22 to 26 
inches. This will, of course, greatly increase the economy of the 
plant and allow the heated feed water to be returned to the boiler. 

The water table is usually made of wooden slats placed in the 
ground near the plant. After trickling over the slats and becoming 
cooled by the air, it collects in the bottom of the reservoir and is then 
pumped into the condenser. 

Amount of Cooling Water Per Pound of Steam. Besides con- 
densing the steam, the injection water cools it still further, so that 
more than merely the latent heat is removed from it. If exhaust 
steam enters the condenser at a temperature t u it contains a certain 
amount of heat, known as total heat at temperature t v If it is con- 
densed and cooled to a temperature t 2 , at which it leaves the con- 
denser, it then contains a certain amount of heat, known as total 
heat at temperature t 2 . 

If A represents the total heat at ti and B represents the heat 
of the liquid at t 2 , then the heat given up by one pound of condensed 
steam is equal to (A—B) British Thermal Units, provided the 
exhaust that enters the condenser is dry saturated steam. If C is 
the temperature of the injection or cooling water and D is the tem- 
perature of the discharge water, then every pound of cooling water 
absorbs approximately one British Thermal Unit for every degree 
rise in the temperature, or we may say that the heat absorbed is 
equal to (D—C) British Thermal Units per pound of cooling water. 
Then it will take as many pounds of water W to absorb (.4—2?) 
heat units as (D — C) is contained in (A — B) . This may be expressed 
thus 

w= {A - B) 



(D-C) 



Therefore, W represents the number of pounds of water required 
per pound of steam condensed. 

Example 1. Suppose steam is expanded in an engine to 4 pounds abso- 
lute pressure. If the initial temperature of the cooling water is 45 degrees, 
and the condenser is of the surface type, discharging water at 120 degrees, 



138 STEAM ENGINES 

and the temperature of the condensed steam is 130 degrees, how many pounds 
of cooling water are required per pound of steam? 

Solution. By consulting the steam tables, we find the total heat of 
steam at 4 pounds pressure to be 1126.5 British Thermal Units. The heat 
of the liquid in the condensed steam at 130 degrees is 98.0 British Thermal 

Units. Then 

1126.5-98.0 



W = 



120-45 
13.71 pounds 



Example 2. Suppose steam at 6 pounds absolute pressure exhausts 
into a jet condenser. The temperature of the injection water is 50 degrees 
and the discharge is 120 degrees. How many pounds of water are necessary 
to condense 8 pounds of steam? 

Solution. In the jet condenser the temperature of the condensed steam 
and the discharge water is the same. We find from the steam tables that the 
total heat of steam at 6 pounds absolute is 1133.6 British Thermal Units, and 
the heat of the liquid in the condensed steam at 120 degrees is 88.0 British 
Thermal Units. Then as before. 

1133.6-88.0 
120-50 
= 14.94 
Therefore, 8 pounds of water will require 14.94X8, or 119.52 pounds. 

The above calculation can not be relied upon to any great 
extent for we seldom know the true condition in the condenser, and 
it would be of little value to us if we did know, as the exact condi- 
tion will change considerably. In practice it is customary to allow 
for about twice as much water as the above calculation would require. 
These figures give us a fair idea of the necessary sizes of the pipes 
and passages leading to the condenser, and give a basis for estimating 
the dimensions of the air pump. 

Cooling Surface in Surface Condensers. The amount of sur- 
face required to condense the steam in surface condensers depends 
upon the conductivity of the metal, the condition of the tubes and 
their thickness, and the difference in temperature between the two 
sides. The tubes of a condenser are much thinner than boiler tubes, 
hence we might expect them to be more efficient in condensing the 
steam than the boiler tubes are in evaporating water. It has been 
found in actual practice, that a surface condenser receiving cqoling 
water at 60 degrees and discharging it at 120 degrees will condense 
from 10 to 20 pounds of steam per square foot of the tube surface per 
hour. An average of 13 pounds per square foot of surface per hour 



STEAM ENGINES 139 

is considered a fair one. With exhaust pressure from 6 to 30 pounds 
absolute, it has been found that an allowance of 1.5 to 3.0 square 
feet of cooling surface per indicated horsepower is sufficient, when 
the initial temperature of cooling water is 60 degrees and the final 
temperature is 120 degrees. 

It is evident that the amount of surface will depend upon the 
quantity of steam used per hour by the engine, the pressure and 
temperature of the exhaust, and the temperature of the cooling 
water and discharge. There must also be an allowance for ineffi- 
cient work after the condenser has become fouled with service. All 
these conditions make the problem so uncertain that calculations 
by means of formulas are likely to be untrustworthy, and it is best 
at all times to make estimates from the figures given for similar 
conditions in actual service. 

Feed Water Heaters. In many places where water is expensive 
and the condensing engines can not be run economically, a very 
considerable saving can be effected either by allowing the exhaust 
steam to condense into a feed water heater, thus saving the heat 
that would otherwise be wasted, or by using the exhaust steam for 
heating purposes. Of course in such cases the steam consumption 
of the engine is high, but if proper allowance is made for the heat 
used for other purposes, the actual fuel consumption rightfully 
charged to the engine is not excessive. If the feed water is heated 
by waste gases, then the gain belongs to the boiler and not to the 
engine. 

ANALYSIS OF ENGINE MECHANISMS 
CRANK EFFORT 

In the steam engine the steam exerts a pressure on the crank 
pin through the piston rod and connecting rod. When the crank is 
at the dead center, the entire pressure is on the bearing of the crank 
shaft, and there is no tendency to turn the crank. As the crank pin 
moves from the dead center, the tendency increases until it reaches 
a maximum and then decreases until, at the other dead center, it is 
zero again. If the connecting rod were of infinite length and steam 
were admitted throughout the whole stroke, the maximum tendency, 
or the maximum turning moment as it is called, would occur with 
the crank at right angles to the line connecting the dead points. 



140 STEAM ENGINES 

Variable Thrust. In the actual engine the thrust along the 
rod is constantly varying even though the pressure on the piston 
remains the same. This is due to the angularity of the connecting 
rod. The turning moment is always equal to the thrust along the 
connecting rod multiplied by the perpendicular distance from the 
connecting rod to the center of the shaft. If the steam pressure on 
the piston remains constant, the maximum turning moment occurs 
when the connecting rod is at right angles to the crank, for in this 
position the perpendicular distance from the rod to the center of the 
shaft is a maximum and equal to the length of the crank; and, as 
the rod makes its greatest angle with the line connecting the dead 
center at this point, the thrust along it will also be a maximum. If 
the cut-off is very early, one-quarter stroke for instance, the maxi- 
mum thrust along the rod will occur earlier than at the point pre- 
viously mentioned, but the leverage of the force will be less, so that 
really there will be little change in the point of maximum turning 
moment no matter where the cut-off may occur. 

Diagrams. To represent this turning moment, diagrams of 
crank effort may be drawn, with rectangular co-ordinates, having 
the crank angles represented as abscissas and the turning moments 
corresponding to these angles as ordinates. 

FLYWHEEL 

Besides the thrust of the connecting rod there must be taken 
into account friction and the inertia of the reciprocating parts. At 
first this may be thought of small consequence but with a fairly 
heavy piston and connecting rod it is obvious that at high speed the 
momentum would be great. In the case of a vertical engine, on 
the up stroke the steam must lift this heavy mass and impart a very 
considerable velocity to it, while on the down stroke the acceleration 
of the mass is added to the steam pressure. This makes the effective 
force on the up stroke less than that due to the actual steam pres- 
sure, and greater on the down stroke. 

Function. In the case of a horizontal engine it is evident that 
while the piston can push the crank around during part of the stroke, 
and pull it along during another part, yet at the end of the stroke 
the pressure on the piston, no matter how great, can exert no turn- 
ing moment on the shaft. Therefore, if some means is not pro- 



STEAM ENGINES 



141 



vided for making the shaft turn past these points without the assist- 
ance of the piston, it may stop. This means is provided in the 
flywheel which is merely a heavy wheel placed on the main shaft. 
On account of the momentum of the flywheel it can not be stopped 
quickly and therefore carries the shaft around until the piston can 
again either push or pull. 

Size of Wheel. If a long period be considered, the mean effort 
and the mean resistance must be equal; but during this period there 
are temporary changes of effort, the excesses causing increase of 
speed. To moderate these fluctuations several methods are employed. 

The turning moment on the shaft of a single cylinder engine 
varies, first, because of the change in steam pressure, and second, on 
account of the angularity of the connecting rod. Before the piston 
reaches mid-stroke the turning moment is a maximum, as shown by 




Fig. 84. 



Graphical Representation of Turning Moment of Crank Shaft of a Single- 
Cylinder Engine for One Stroke 



the curve, Fig. 84. Near the ends of the stroke the turning moment 
diminishes and finally becomes zero. This, of course, tends to cause 
a corresponding change in the speed of rotation of the shaft. In 
order to have this speed as nearly constant as possible and to give 
a greater uniformity of driving power, the engine may be run at high 
speed. By this means the inertia of the revolving parts, such as 
the connecting rod and crank, causes less variation. When the work 
to be done is steady and always in the same direction, a heavy fly- 
wheel may be used. The heavier the flywheel, the steadier will 
be the motion. It is desirable, of course, in all engines to have steady 
motion, but in some cases it is more important than in others. For 
instance, in electric lighting plants it is necessary that the machinery 
shall move with almost perfect steadiness. It is undesirable to use 
larger wheels than are absolutely necessary, because of the cost of 
the metal, the weight on the bearings, and the danger from bursting. 



142 STEAM ENGINES 

Methods of Reducing Size. If the turning moment which is 
exerted on the shaft from the piston could be made more regular 
and if dead points could be avoided, it would be possible to get a 
steadier motion with a much smaller flywheel. 

If the engine must be stopped and reversed frequently, two or 
more cylinders are used, being connected to the same shaft. The 
cranks are placed at such angles that when one is exerting its mini- 
mum rotative effort, the other is exerting its maximum, or when one 
is at a dead center, the other is exerting its greatest effort. These 
cylinders may be identically the same in dimension as is the case 
with most hoisting engines and with many locomotives; or the engine 
may be compound or triple expansion. This arrangement is also 
used on engines for mines, collieries, and for hoisting of any sort 
where ease of stopping, starting, and reversing are prerequisites. 
Simple expansion engines with their cranks at right angles are usually 
spoken of as being coupled. 

The governor adjusts the power of the engine to any large varia- 
tion of the resistance. The flywheel has a duty to perform which 
is similar to that of the governor. It is designed to adjust the effort 
of the engine to sudden changes of the load which may occur during 
a single stroke. It also equalizes the variation in rotative effort on 
the crank pin. The flywheel absorbs energy while the turning 
moment is in excess of the resistance, and restores it while the crank 
is at or near the dead points. During these periods the resistance is 
in excess of the power. 

Action of Flywheel. The action of the flywheel may be repre- 
sented as in Figs. 84 and 85. It will be noticed that in Fig. 84, the 
curve of the crank effort runs below the axis toward the end of the 
stroke. This is because the compression is greater than the pressure 
near the end of expansion, and produces a resultant pressure on the 
piston. In Fig. 85 the effect of compression has been neglected. 
Let us suppose that the resistance, or load, is uniform. In Fig. 84, 
the line A B is the length of the semi-circumference of the crank pin. 
or the circumferential distance the crank pin moves during one 
stroke. The curve A M D B is the curve of turning moment for 
one stroke. M N is the mean ordinate and, therefore, A E F B 
represents the constant resistance. The effort and resistance must 
be equal if the speed is uniform; hence the area A E F B equals 



STEAM ENGINES 143 

AM DO B. Then area A E M plus area F B equals area MDO. 
At A the rotative effort is zero because the crank pin is at the dead 
point and from A to N, the turning moment is less than the resist- 
ance. At N the resistance and the effort are equal. From N to P 
the effort is in excess of the resistance. At P the effort and the 
resistance are again equal. From P to B the resistance is greater 
than the effort. In other words, from A to N the work done by 
the steam is less than the resistance. This shows that the work rep- 
resented by the area A E M must have been done by the moving 
parts of the engine. From N to P the work done by the steam is 
greater than the resistance, and the excess of energy is absorbed by 
or stored in the moving parts. From P to the end of the stroke the 
work represented by the area F B is done on the crank pin by the 
moving parts. 



Fig. 85. Simultaneous Crank Effort Curves of Two Engines Acting at Right 
Angles to Each Other 

It is known that energy is proportional to the square of the 
velocity from the formula 

in which E is energy in foot pounds, W is weight in pounds, V is 
velocity in feet per second, and g is acceleration of gravity in feet per 
second 2 . Hence as W and g remain the same, the velocity must be 
reduced when the moving parts are giving out energy and increased 
when receiving energy. Thus it is seen that the action of the crank 
pin is to move slowly, then more rapidly. The weight of the 
revolving parts of an engine is not sufficient to absorb sufficient sur- 
plus energy, hence a heavy flywheel is used. 

In case there are two engines at right angles, two crank effort 
curves may be drawn, as shown in Fig. 85. The mean ordinate A E 
is equal to the mean or constant resistance. There are two minimum 
and two maximum velocities in one stroke. The diagram shows 



144 STEAM ENGINES 

that the variation is much less than for a single cylinder, hence a 
lighter wheel may be used. 

Calculations of Mass. The weight of the flywheel depends upon 
the character of the work done. For pumping engines and ordinary 
machine work the effort need not be as constant as for electric light- 
ing. In determining the proper weight of a flywheel the diameter 
of the wheel must be known. If the wheel is too large, the high linear 
velocity of the rim will cause too great a centrifugal force and the 
wheel will not be safe. In practice, about 6,000 feet per minute is 
taken as the maximum linear velocity of cast-iron wheels. When 
made of wood and carefully put together the velocity may be taken 
as 7,000 to 7,500 feet per minute. 

The linear velocity of a wheel is expressed in feet per minute 
by the formula V ' = 2n R N, or tt D N, in which V is velocity in feet 
per second, R is radius of wheel in feet, D is diameter of wheel in 
feet, and N is revolutions per minute. 

Then if a wheel runs at 100 revolutions per minute, the allow- 
able diameter would be obtained from the equation 

6000 = 3.1416 X D X 100 
Therefore 

6000 
" 3.1416X100 
= 19.1 feet 
If a wheel is 12 feet in diameter the allowable speed is found to be 
V 



N=- 

nD 



6000 



3.1416X12 

= 159 revolutions per minute 

It is usual to make the diameter less than the calculated diameter. 

Having determined the diameter, the weight may be calculated 

by several methods. There are many formulas to obtain this result 

given by various authorities, one formula being 

TT7 Cxd 2 Xb 

W = 

D 2 XN 2 

in which W is weight of rim in pounds; d is diameter of cylinder in 

inches; b is length of stroke in inches; D is diameter of flywheel in 



STEAM ENGINES 1 15 

feet; N is number of revolutions per minute; and C is a constant 
having a value which varies for different types of engines and 
for different conditions as follows: 

Slide valve engines, ordinary work C= 350,000 

Corliss engines, ordinary work C = 700,000 

Slide-valve engines, efectric lighting C = 700,000 

Automatic high speed engines C = 1,000,000 

Corliss engines, electricjighting C = 1,000,000 

Example 1. Find the weight of a flywheel rim for an automatic high 
speed engine used for electric lighting. The cylinder is 24 inches in diameter; 
the stroke is 2 feet. It runs at 300 revolutions per minute, and the flywheel 
is to be 6 feet in diameter. 
Solution. 

1000000 X (24)2X24 
36X90000 
= 4266 pounds 
Example 2. A plain slide valve engine for electric lighting is 20 inches 
X 24 inches. It runs at 150 revolutions per minute. The flywheel is to be 
8 feet in diameter. What is the weight of its rim? 

Solution. 700000X400X24 

W = — ■ 

64X22500 

= 4666 pounds 

The weight of a flywheel is considered as being in the rim. The 
weight of the hub and arms is simply extra weight. Then, if the 
weight of the rim and its diameter be known, the width of the face 
and thickness of the rim can be found. Assume the given diameter 
to be the mean of the diameter of the inside and outside of the rim. 
Let b equal width of face in inches ; t equal thickness of rim in inches ; 
d equal diameter of flywheel in inches; and .2607 equal weight of 1 
cubic inch of cast iron. Then 

W=. 2607 XbXtXnd 
= bXtX.819d 

Example 3. Suppose the rim of a flywheel weighs 6,000 pounds, is 9 
feet in diameter, and the width of the face is 24 inches. What is the thickness 
of the rim? 

Solution. ^ 

t = . 819 db 

6000 
".819X108X24 
= 2.83 inches 
In this case the rim would probably be made 2^f inches thick. The total 
weight, including hub and arms, would probably be about 8,000 pounds. 



146 STEAM ENGINES 



GOVBRNOR 



The load on an engine is never constant, although there are 
cases where it is nearly uniform. While the engine is running at 
constant speed, the resistance at the flywheel rim is equal to the 
work done by the steam, disregarding friction. If the load on the 
engine is wholly or partially removed and the supply of steam con- 
tinues undiminished, the force exerted by the steam will be in excess 
of the resistance. Work is equal to force multiplied by distance; 
hence, with constant effort, if the resistance is diminished, the dis- 
tance must be increased. In other words, the speed of the engine 
will be increased, and the engine will "race." Also, if the load 
increases and the steam supply remains constant, the engine will 
"slow down." 

It is evident, then, that if the speed is to be kept constant 
some means must be provided so that the steam supply shall at all 
times be exactly proportional to the load. This is accomplished by 
means of a governor. 

Methods of Action. Steam-engine governors act in one of two 
ways (1) they may regulate the pressure of steam admitted to the 
steam chest, or (2) they may adjust the speed by altering the amount 
of steam admitted. Those which act in the first way are called 
throttling governors, because they throttle the steam in the main 
steam pipe. Those of the latter class are called automatic cut-off 
governors, since they automatically regulate the point of cut-off. 

Theoretically, the method of governing by throttling the steam 
causes a loss in efficiency, but the throttling superheats the steam, 
thus reducing cylinder condensation. By the second method the 
loss in efficiency is very slight, unless the ratio of expansion is already 
great, in which case shortening the cut-off causes an increasing 
cylinder condensation. 

Control by Centrifugal Force. In most governors of the throt- 
tling type and those applied to Corliss engines, centrifugal force 
counteracted by some other force is employed. A pair of heavy 
masses (usually iron balls or weights) are made to revolve about a 
spindle, which is driven by the engine. When the speed increases, 
the centrifugal force increases and the balls tend to fly outward, 
that is, they revolve in a larger circle. The controlling force, which 
is usually gravity or springs, is no longer able to keep the balls in 



STEAM ENGINES 147 

their former path. When, therefore, the increase is sufficiently 
great, the balls in moving outward act on the regulator, which may 
throttle the steam or cause cut-off to occur earlier. 

With the throttling governor, a balanced throttle valve is placed 
in the main steam pipe leading to the valve chest. If the engine 
runs faster than the desired speed, the balls are forced to revolve at 
a higher speed. The increase in centrifugal force will cause them to 
revolve in a larger circle and in a higher plane. By means of levers 
and gears, the spindle may be forced downward, thus partially clos- 
ing the valve. The engine, therefore, takes the steam at a low 
pressure, and consequently the speed falls slightly. 

Similarly, if the load is increased, the engine slows down, caus- 
ing the balls to drop and open the valve more widely; steam at 
higher pressure is then admitted and the speed is increased to the 
regular number of revolutions. 

With the Corliss or other four-valve engines, the governor acts 
differently. Instead of throttling the steam in the steam pipe, 
the governor is connected to the releasing gear by rods. An increase 
of speed causes the releasing gear to unhook the disengaging link 
earlier in the stroke. This causes earlier cut-off, which of course 
decreases the power and speed, since the amount of steam admitted 
is less. If for any reason the load increases, the governor causes 
the valves to be held open longer. The cut-off, therefore, occurs 
later in the stroke. 

Pendulum Governor. One of the most common forms of gov- 
ernor is similar to that invented by James Watt. It is called from 
its appearance the pendulum governor and is illustrated in principle 
in Fig. 86. To consider the theory of the pendulum governor, the 
masses of the balls are assumed to be concentrated at their centers 
and the rods are made of some material having no weight. 

When the governor is revolving about its axis at a constant 
speed, the balls revolve in a circle having a radius r. The distance 
from this plane to the intersection of the rods, or the rods produced, 
is called the height and is equal to h. 

If the balls revolve faster, the centrifugal force increases, r 
becomes greater, and h diminishes. The mathematical expression 
for centrifugal force is Wv 2 



148 



STEAM ENGINES 



in which F is force in pounds; W is weight of one ball in pounds: v is 
velocity in feet per second; g is acceleration due to gravity; and r is 
radius in feet. From the above equation it is seen that force varies 
inversely as the radius. 

While the pendulum is revolving, centrifugal force acts hori- 
zontally outward and tends to make the balls fly from the center; 
and the action of gravity tends to make the balls drop downward. In 
order that the balls shall revolve at a certain height, the moments 
of these two forces about the point of suspension must be equal, or 




Diagrams Showing Action of Pendulum Governor 



the weight of the balls multiplied by their distance from the center 
must equal the centrifugal force multiplied by the height, or 

WXr = Fxh 
from which 

Substituting value of F just given, we have 

A JL 

r ~W? 



gr 



Therefore, 



h = 



gr 



Now since v, the linear velocity of a point revolving in the circum- 
ference of a circle, is expressed as 2 u r N' feet per second, where N' 



STEAM ENGINES 140 

is revolutions per second, this value may be substituted in the 
above formula, giving 



4^ 2 r 2 (iV / ) 2 

g 

4;r 2 (N'Y 



and since the values of g and it. are known, the formula may be 
written 

32.16 



4X3.1416 2 X(iV') 2 
.8146 



(NJ 



feet 



9.775 . . 
= inches 

If it is desired to use N, the r.p.m., instead of N' t the r.p.s., the 
former may be substituted in the formula by multiplying the fraction 

by 60 2 , or 3600, giving 

. 2932.56 , 
h= teet 

iV 2 

35190.7 . . 
= inches 

N 2 

From the above formula it is evident that the height is inde- 
pendent of the weight of the balls or the length of the rod, depending 
entirely upon the number of revolutions. The height varies inversely 
as the square of the number of revolutions. 

The ordinary pendulum governor is not isochronous, that is, 
it does not revolve at a uniform speed in all positions, the speed 
changing as the angle between the arms and spindle changes. 

Fly=Ball Governor. The early form consisted of two heavy 
balls suspended by links from a pin connection in a vertical spindle, 
as shown in Figs. 87 and 88. The spindle is caused to revolve by 
belting or gearing from the main shaft, so that as the speed increases, 
centrifugal force causes the balls to revolve in a circle of larger and 



flsm 



150 



STEAM ENGINES 



larger diameter. The change of position of these balls can be made 
to affect the controlling valves so that the admission or throttling 
will vary with their position. With this governor it is evident that 
for a given speed of the engine there is but one possible position for 
the governor, consequently one definite amount of throttling or one 
point of cut-off, as the case may be. If the load varies, the speed of 
the engine will change. This causes the position of the governor balls 
to be changed slightly, thus altering the pressure. But in order that 
the pressure or cut-off shall remain changed, the governor balls must 
stay in their new position. That is to say, the speed of the engine 





Fig. 87. Simple Type of Fly- 
Ball Governor 



Fig. 88. Later Type of Fly- 
Ball Governor 



must be slightly changed. Thus with the old ball governors there 
was a slightly different speed for each load. This condition has been 
greatly improved by various modifications until now such governors 
give excellent regulation. 

While the engine is running with a light load, the valve con- 
trolled by the governor will be open just enough to admit steam at 
a pressure that will keep the engine running at a given speed. Now 
if the engine is heavily loaded, the throttle valve must be wide open. 
The change of opening is obtained by a variation in the height of the 
governor, which is caused by a change of speed. Thus it is seen that 
the governor can control the speed only within certain limits which 
are not far apart. The difference in the extreme heights of the gov- 
ernor must be sufficient to open the throttle its entire range. In 



STEAM ENGINES 



l.-l 



TABLE II 

Heights of Governor for Different Speeds of Engine 



dumber of Revolutions 
Per Minute 


Height in Inches 


Variation of Heighl in 
Inches 1 Per Cenl 


250 


. 563 


.0225 


200 


.879 


.035 


175 


1.149 


.046 


150 


1 . 564 


.062 


125 


2.252 


.090 


100 


3.519 


.140 


75 


6.256 


.250 


50 


14.076 


.563 



most well-designed engines, equipped with a throttling governor, 
the speed will not vary more than 4 per cent, that is, 2 per cent above 
or below the mean speed. 

From the formula h = 77~~> tne heights corresponding to 

given speeds can be computed as shown in the second column of 
Table II. The third column is the variation in height for a speed 
variation of 4 per cent or 2 per cent either above or below the 
mean. 

Disadvantage of Ordinary Fly-Ball Type. From Table II it 
will be seen that for a considerable variation of speed there is but 
slight variation in the height of the governor, this being too small to 
control the cut-off or throttling mechanism throughout the entire 
range. Also for high speeds the height of the governor is so small 
that it would be difficult to construct it. 

Other disadvantages of the fly-ball governor are as follows: 
It is apparent that the valves must be controlled by the weight of 
the governor balls. In large engines this requires very heavy balls 
in order to quickly overcome the resistance of the valves. But these 
large balls have considerable inertia and will therefore be reluctant 
to change their speed with that of the engine. The increased weight 
will also increase the friction in the governor joints and the cramp- 
ing action existing when the balls are driven by the spindle will 
increase this friction much further. All these things tend to delay 
the action of the governor, so that in all large engines the old-fash- 



152 



STEAM ENGINES 



ioned governor became sluggish. The balls had to turn slowly 
because they were so heavy; this was especially troublesome in high- 
speed engines. 

Porter Improved Type. To remedy these defects the weighted 
or Porter governor, Fig. 89. was designed. It has a greater height 
for a given speed, and the variation in height for a given variation 
of speed is greater and, consequently, more sensitive. By increas- 
ing this variation in height, the sensitiveness is increased. Thus, if 
a governor running at 50 revolutions has a variation in height of .57 
inch, it is not as sensitive as one having a variation of 1 inch for 
the same speed. 

In the weighted governor, the weight is formed so that the center 
of gravity is in the axis. It is placed on the spindle and is free to 

revolve. The weight adds to the weight 
of the balls, and thus increases the mo- 
ment of the weight. It does not, how- 
ever, add to the centrifugal force, and 
hence the moment of this force is un- 
changed. It may then be said that the 
weight adds effect to the weight of the 
governor balls but not to the centrifugal 
force, and as a consequence the height of 
the governor for a given speed is in- 
creased. If W equals the weight of the 
ball as before, and W equals one-half the 
added weight, the equated moments are 

(W+W) r =Fh 

Substituting for F its value obtained from the formula, p. 147, we have 

(Wv 2 \ 




TT 



Fig. 89. Porter Improved Type 
of Fly-Ball Governor 



(W+W)r*g 



WX^r^N'f 



(W+W) 

w 



X 



(— — ) 

^(47^ 2 (iV , ) 2 / 



STEAM ENGINES 



153 



Since it is known that 



.8146 






/W-\-W'\ .8146 

= V1F ) X (N'y 



Hence the height of a weighted governor is equal to the height of 

a simple pendulum governor multiplied by ^ — — ), or ^1+— J- 

For instance, if the height of a simple pendulum is 10 inches and 





Fig. 90. Waters Governor with 
Safety Stop 



Fig 91. Waters Spring Type of Fly- 
Ball Governor 



the weight of the balls equal to the added weight, the height of 
the weighted governor will be 



xio 



= 2X10 
= 20 

Thus it is evident that if a weight equal to the combined weight 
of the balls is added, the height of the governor will be doubled. 
If the belt driving the governor slips off or breaks, the balls will 



154 



STEAM ENGINES 



cSd 



drop, with the result that the engine will "run away." To diminish 
this danger many governors are provided with some kind of safety 
stop which closes the valve when the governor loses its normal 
action. Usually a trip is provided which the governor does not 
touch in its normal positions, but which will be released if the balls 
drop down below a certain point. 

Spring Type. In many cases a spring is used in place of the 
weight. This type of governor is frequently used on throttling 

engines, and it consists of a pen- 
dulum governor with springs 
added to counteract the centrif- 
ugal force of the balls. Thus the 
height and sensitiveness are in- 
creased. Fig. 90 shows the ex- 
terior view of a Waters governor 
and Fig. 91 shows the same 
governor having the safety stop. 
In this governor the weights are 
always in the same plane, the 
variation in height being due to 
the action of the bell-crank levers 
connecting the balls and spindle. 
When the balls move outward, 
the spindle moves downward and 
tends to close the valve. The 
governor balls are caused to re- 
volve by means of a belt and bevel 
gears. The valve and seat are 
valve is a hollow cylinder with 
The seat is made in four 




Fig. 92. 



Section of Valve and Valve Seat of 
Waters Governor 



shown in section in Fig. 92. The 

three ports through which steam enters. 

parts, that is, there are four edges that the steam passes as it enters 

the valve. The valve, being cylindrical and having steam on both 

sides, is balanced, and because of the many openings only a small 

travel is necessary. 

Shaft Governor. Usually some form of pendulum governor 
is used for throttling engines. For governing an engine by varying 
the point of cut-off, shaft governors are generally used, although the 
Corliss and some other engines use pendulum governors for this pur- 



STEAM ENGINES 



155 



pose. Cut-off governors, which are called shaft governors because 
they are placed on the main shaft, are made in many forms, but their 
essential features are the same. Two pivoted masses or weights 
are arranged symmetrically on opposite sides of the shaft and their 
tendency to fly outward when the speed increases is resisted by 
springs. When in action the outward motion of the weights causes 
the admission valve to close earlier, and the inward motion causes 
it to close later. This change is effected by altering the position of 




Fig. 93. Diagram Showing Action of Buckeye Shaft Governor 



the eccentric, either by changing the eccentricity or the angular 
advance. 

Shaft governors are made in a great variety of ways, no two 
being exactly alike. If the principles of a few types are understood, 
it is easy to understand others. 

Buckeye Type. The valve of the Buckeye engine is hollow and 
of the slide valve type. The cut-off valve is inside. The change of 
cut-off is due to the alteration of the angular advance, the arrange- 
ment of the parts which effect this alteration being shown in Fig. 93. 
A wheel which contains and supports the various parts of the gov- 



156 



STEAM ENGINES 



ernor is keyed to the shaft. Two arms, having weights A A at the 
ends, are pivoted to the arms of the wheel b b. The ends having the 
weights are connected to the collar on the loose eccentric C by means 
of rods B B. 

When the weights move to the position indicated by the dotted 
lines, the eccentric is turned on the shaft about a quarter of a revo- 
lution in the direction in which the engine runs, that is, the eccentric 
is advanced, or the angular advance is increased; this makes cut-off 
occur earlier, as shown by the table presented in "Valve Gears." If 
the engine had a single plain slide valve, the variation of the angular 




Fig. 94. Diagram Showing Action of Straight-Line Type of Shaft Governor 

advance would produce too great a variation of lead; but as this 
engine has a separate valve for cut-off, admission is not altered by 
the cut-off valve. 

The springs F F balance the centrifugal force of the weights; 
the weights A A are varied to suit the speed; and the tension on 
the springs is altered by means of the screws c c. Auxiliary springs 
are added in order to obtain the exactness of regulation necessary 
for electric lighting. These springs tend to throw the arms outward, 
but act only during the inner half of this movement. 

Straight-Line Type. Fig. 94 shows the governor of the Straight- 
line engine. It has but one ball B, which is linked to the spring S 



STEAM ENGINES 



157 



and to the plate DE< on which is the eccentric (7, When the ball 
flies outward in the direction indicated by the arrow F, the eccentric 
is shifted about the pivot 0, the links moving in the direction of the 
arrow //. The ball is heavy and at a considerable distance from 
the center, hence it has a great centrifugal force and the spring must 
be stiff. The governor of the Buckeye engine alters the cut-off by 
changing the angular advance, while the Straight-line engine gov- 
ernor changes the travel of the valve. The latter type of valve is 
very common. 

Inertia Form. The well-known Rites inertia governor, Fig. 95, 
is a form of shaft governor largely used for certain types of engines. 
This governor regulates the 
speed of the engine by shifting 
the eccentric, thus changing 
the valve travel and increas- 
ing or decreasing the angular 
advance, depending on the 
speed conditions. It differs in 
its operation from the centrif- 
ugal shaft governor previous- 
ly considered, in that it makes 
use of the inertia of two large 
weights instead of centrifugal 
force. To understand this 
action, it first becomes nec- 
essary to know something Fig - 95 ' m& %^ H °Goil?nor nertia Type ° f 
about its construction. 

The governor consists essentially of a heavy arm A pivoted at 
E to the flywheel. This arm carries two heavy weights at B. The 
eccentric D is fastened to the arm by three countersunk screws, as 
shown, and moves with reference to the engine shaft whenever the 
weights B cause the arm A to move about its pivot point. Fas- 
tened to the flywheel arm and the governor arm A is the spring C, 
which brings the arm A back to its normal position when the engine 
is not operating. This spring also has certain other functions to 
perform in the operation of the governor. 

The action of the governor is such that the valve experiences 
very much the same movement as in the centrifugal governor. As 




158 STEAM ENGINES 

the engine speeds up, the tendency of the heavy arm A is to lag behind 
the flywheel. This lagging action controls the position of the eccen- 
tric so that the valve travel is reduced, thus limiting the amount of 
steam that enters the cylinders. If, after the engine is operating at 
a uniform rate of speed, an increase of load suddenly occurs, the 
motion of the engine shaft and flywheel will be slightly retarded and 
the engine will commence to "slow down." On account of the energy 
stored up in the governor arm and the weights BB, they will not be 
so quickly affected, hence the governor w T ill be moving slightly faster 
than the shaft. As a result the eccentric position with reference to 
the shaft will be changed, and the valve travel increased, thus per- 
mitting more steam to enter the cylinder, increasing the power com- 
mensurate with the added load. If for any reason the engine takes 
a sudden spurt in speed, the tendency of the governor is to fall back- 
ward, so to speak; and if the engine is suddenly slowed down for any 
cause, the tendency of the governor is to plunge forward; hence the 
valve travel is shortened or lengthened according to which action 
takes place. This type of governor gives very close regulation when 
properly constructed. 

ERECTION AND OPERATION OF STEAM ENGINES 

The limited scope of this work will not permit of an exhaustive 
study of these two important details — the erection and operation of 
steam engines; only the general principles governing each will be 
pointed out. 

ERECTION 

Foundations. When about to erect an engine the first requisite 
is the foundation, the character of which will, of course, depend upon 
the type and the size of the engine. It should be built according to 
plans submitted by the engine builders, no changes of material con- 
sequence being made without the approval of the builders. It 
should be neither connected with nor in close proximity to any sup- 
porting column or columns of the building, as vibrations of the engine 
will be transmitted to the building which might prove to be disas- 
trous. The foundation should be built upon a solid bottom, but if 
this is not obtainable at the depth required by the foundation plans, 
the base of the foundation should be extended in all directions in 



STEAM ENGINES 159 

order that the bearing surface may be increased. In the case of the 
horizontal engines the nearer the center of gravity of the foundation 
is placed to the center line of the engine, the more effective will be 
the foundation. In such cases, therefore, it is preferable to have an 
extended bearing surface rather than one of considerable depth. The 
foundation bolts and washers should be carefully located in accord- 
ance with the furnished plans. A space of one inch or more should 
be left around each of the foundation bolts. This may be obtained by 
using pieces of short iron pipe or old boiler tubes around the bolts, 
care being taken that they do not extend above the foundation, so 
as to prevent the proper tightening of the bolts after the engine is 
placed in position. After the engine is properly set, the space left 
around the foundation bolts should be filled with the best cement 
mortar, so as to insure their permanency. The foundation should 
be a solid one and built of brick, stone, or concrete. 

Brick. When brick is used, a hollow square effect may be con- 
structed and the open space filled with a mixture of concrete, con- 
sisting of one part cement and three parts sand and gravel. 

Concrete. When making a concrete foundation, suitable forms 
must first be constructed to receive the concrete. Crushed stone or 
clean gravel or both may be used, care being taken to wash the gravel 
free of all clay. A good mixture for ordinary foundations is one hav- 
ing the proportions: 1:2}: 5. That is, 1 barrel, or 4 bags, cement, 
2| barrels, or 9.5 cubic feet, of sand, and 5 barrels, or 19 cubic feet, 
of gravel or stone. If the foundation is to be waterproof, careful 
consideration must be given to the proportioning of the mixture. If 
the foundation covers considerable area and is not very deep, the 
mixture should be richer in cement; if, however, the foundation is 
very deep, a poorer mixture may be used at the bottom and a richer 
one near the top. 

The cement, gravel or stone, and sand should first be thoroughly 
mixed in the dry state and the water added while the mixing process 
continues until the mass is well mixed and thoroughly wet. After the 
mixing is complete, the concrete should be laid in layers from 6 to 9 
inches deep and well rammed until solid. The ramming of the concrete 
is an absolute necessity in order that a solid foundation may be secured. 

When the foundation has been completed in accordance with 
the furnished plans, sufficient time must elapse before any machinery 



160 STEAM ENGINES 

is placed thereon in order to insure a proper setting of the cement. 
When the concrete has set sufficiently, it should be inspected to see 
that no omissions or errors have been made, after which the engine 
may be unpacked and prepared for setting. If the foundation is a 
large one, an inspector should be on hand at all times to follow the 
work and see that no errors are made. 

Setting the Engine. Upon the accuracy and thoroughness of 
the setting of the engine, in a large measure depends its successful 
operation as to smoothness and efficiency of running. In this proc- 
ess there are a great many things to be considered. First, the base 
and sub-base must be carefully cleaned and set in position. Next, 
the crank shaft, cylinders, piston, crosshead valves, and other details 
must be carefully placed in position and alignment made according 
to the plans of the builders. As all of these details require skill, an 
inexperienced person should not attempt the setting up of an engine. 
It is always preferable, when possible, to obtain an experienced man 
from the engine builders. 

Installation of Attachments. In addition to the erection and 
setting of the engine proper there are various attachments and aux- 
iliaries that require care and skill in their proper installation. The 
steam and exhaust piping as well as the cylinder drainage should be 
carefully attended to. The piping should be of ample size, all bends 
should be easy, and gate valves should be used whenever possible. 
The piping should have a gradual fall from the boiler to the engine, 
at or near which should be placed a separator. 

Separator. The separator should be of approved design, and 
care must be taken to carefully provide for drainage in order to insure 
the removal of the water, otherwise the separator might form a 
reservoir for water and thus endanger the engine more with its use 
than without. In addition to being a safeguard against water ham- 
mer, when properly attached, the separator also improves the steam 
economy of the engine, since it removes the most of the entrained 
moisture which is carried from the boiler through the steam 
pipes. 

Exhaust Pipes. The exhaust pipes should be of ample area to 
take care of all exhaust steam, and safeguards should be used to insure 
no backing up of the condensed exhaust into the cylinders. To this 
end, sharp bends should be avoided and gate valves should be used 



STEAM ENGINES 161 

if valves are necessary, as by their use the area of the pipe is less 
reduced than by other forms of valves. Check valves should be 
avoided whenever possible. 

Cylinder Drains. The cylinder drains should be of sufficient 
area to care for all condensed steam in the cylinders and so attached 
to the cylinders and the exhaust pipe or receiver that no pockets 
will be formed for the accumulation of water. In the case of com- 
pound engines the cylinder drains of the high and the low pressure 
cylinders should not be connected together, but separately connected 
to the exhaust or other main drain. In condensing engines the cyl- 
inder drains should always go into the exhaust drain if it is low 
enough to admit of proper drainage. 

OPERATION 

Let us now turn our attention to the operation and manage- 
ment of an engine. It should be borne in mind that many sug- 
gestions as to the proper alignment and adjustment of bearings, the 
adjustment of valves, and the consideration given lubrication will 
be applicable both to the first setting up of the engine and also to the 
daily operation afterwards. 

Competent Engineer a Requisite. The operation of an engine 
should be committed to a careful, skillful, and reliable man. This 
is especially true in the case of modern well-equipped plants which 
represent quite an outlay of capital. In many of the smaller plants, 
however, not much attention is given to the matter and we find, as 
a result, men holding positions as operators who know very little 
about their business. Under such conditions the plants are seldom 
operated efficiently. 

As a suggestion of some of the duties of a man in charge of a 
modern plant, which also suggest the amount of judgment and expe- 
rience required, the following general instructions are presented. 

Care of Bearing Caps. The caps on the main bearings should 
always have sufficient liners underneath to enable the nuts on the 
bearing studs to draw the cap down tightly upon them and not pinch 
the shaft, which should be free to revolve in its bearings without 
unnecessary play. 

The caps should be removed occasionally as conditions demand 
in order to clean out the oil grooves which are chipped in the babbitt 



162 STEAM ENGINES 

metal, as the passages may become clogged with dirt or other for- 
eign matter. 

Adjustment of Connecting Rod Box. In adjusting the connect- 
ing rod box at the crank pin end, the same general rules should be 
observed regarding the liners under the cap — the large nuts drawn 
solidly upon it, the small nuts firmly jammed and the cotter pins 
placed in position. The adjustment of the box should then be 
tested with a lever about 12 inches in length, the adjustment being 
so made that with a lever of this length the operator can easily move 
the end of the connecting rod sufficiently to take up the side play 
between the flanges on the crank pin and the end of the box. The 
adjustment should never be made so close that this side movement 
can not be observed. 

The adjustment of the connecting rod box at the crosshead pin 
should be made by placing the crank on the center nearest the cyl- 
inder; then with a wrench provided for that purpose, slack off both 
wedge screws at the upper and lower sides of the connecting rod, 
and draw the wedge up until it is solid against the box; then slack 
off one screw about a sixth of a turn, and draw up the other so as to 
firmly lock the wedge. 

Lining Up Crosshead. The crosshead should be lined up between 
the guides, while disconnected from the connecting rod. When in 
this condition the crosshead should be so lined that it can be easily 
pulled from one end of the guides to the other with a short lever. 

The crosshead should never be run very close, and should always 
be free enough to allow long and continuous runs without heating 
the guides to the degree that they would be uncomfortably warm 
to the touch. 

When making any adjustments of the crosshead, the operator 
should assure himself that the lock nut which prevents the piston 
rod turning in the boss of the crosshead is securely placed. 

Adjusting Eccentric Strap. The eccentric strap adjustment is 
made by liners placed between the halves of the strap and double 
nutted bolts. When adjustment is necessary, the other end of the 
eccentric rod should be disconnected and, after drawing up the strap 
bolts, it should be tested by giving the strap a half revolution about 
the eccentric. If it is found that the friction between the strap and 
the eccentric is sufficient to support the weight of the rod, the bolts 



STEAM ENGINES 163 

should be loosened and liners replaced until the strap moves freely 
without lost motion. The double nuts should then be locked and 
the cotter pins replaced in the ends of the bolts. 

Governor. The governor should be adjusted to meet the differ- 
ent conditions of speed and steam pressure and the degree of regula- 
tion required. As governors differ so much in design and detail of 
construction, it is not possible to give any general rule for their 
adjustment. The operator, if desired, can usually obtain instruc- 
tions from the engine builder for the particular type of governor 
in question. 

Valve Setting. As a discussion of the setting of the valves and 
their adjustment for wear will be found given in ''Valve Gears," 
no consideration of the subject will be presented here. 

Lubrication. The lubrication of a steam engine, and especially 
of high speed engines, is a very important consideration with both 
the designer and the operator, for it is upon proper lubrication that 
they must largely depend for a constant and satisfactory operation. 
The designer must, therefore, provide ample and efficient facilities 
for lubricating the bearings, cylinders, and valves, whereas the opera- 
tor must use discretion in selecting his lubricants and the amount to 
use after selection has been made. 

Choice of Oils. It might be said that only the best oils should be 
used. Cheap oils are usually considered expensive at any cost and 
should be avoided as they promote excessive wearing of the parts — 
causing noisy operation — and may cause serious cutting of the 
cylinders. There are two general classes of liquid lubricants now 
in the market, namely, mineral and animal oils. There is also a com- 
pounded lubricant which is made up of about 5 to 15 per cent of 
animal matter and the balance of mineral oil. This compound makes 
a very efficient lubricant for some classes of service, as it withstands 
the action of the condensation and adheres to the surface of the cyl- 
inders, thus giving better results than larger quantities of mineral oil. 

In plants where open heaters are used and where the exhaust 
steam is condensed and used for boiler feed water, the compounded 
oils can not be used, on account of the danger of the animal matter 
getting into the boilers and causing considerable trouble. In such 
cases mineral oil must be used, although it may require considerable 
more mineral than compounded oil to accomplish the lubrication. 



164 STEAM ENGINES 

Solid Lubricants. Several solid lubricants are used, such as 
graphite, metalline, soapstone, and fiber graphite. 

Graphite when mixed with certain oils is well adapted for heavy 
pressures. It is especially good for heavy pressures and low veloci- 
ties. Under conditions which require a large amount of cylinder oil, 
a small amount of crystal or flake graphite may be used with good 
results. Care must be exercised, however, if the exhaust steam is 
used for feed water, as the graphite may get into the boilers and 
cause inconvenience and perhaps serious trouble. 

Metalline is a solid compound containing graphite. It is made 
in the form of solid cylinders, which are fitted to the holes drilled 
into the surface of the bearing. When a bearing is thus fitted, no 
other lubricant is necessary. 

Soapstone in the form of powder and mixed with oil or fat is 
sometimes used as a lubricant. Soap mixed with graphite or 
soap-stone is often used where wood is in contact with wood or 
iron. 

A preparation called fiber graphite is used for self-lubricating 
bearings. It is made of finely divided graphite mixed with fibers 
of wood. It is pressed in molds and afterwards fitted to bearings. 

For great pressure at slow speed, graphite, lard, tallow, and 
other solid lubricants are suitable. If the pressure is great and the 
speed high, castor, sperm, and heavy mineral oils are used. 

For low pressure and high speed, olive, sperm, rape, and refined 
petroleum give very satisfactory results. 

In ordinary machinery, heavy mineral and vegetable oils and 
lard oil are good. The relative value of various lubricants depends 
upon the prevailing conditions. Oil that is suitable for one place 
might not flow freely enough for another. 

The quality of oil is of great importance. In many branches of 
industry it is imperative that the machinery run as perfectly as 
possible. On this account and because of the high cost of machinery, 
only first class oil should be used. The cylinder oil especially should 
be high grade, because the valves, piston, and piston rods are the 
most delicate parts of the engine. 

Qualities of a Good Lubricant. From the foregoing brief discus- 
sion of lubricants it will be evident that they must possess certain 
qualities which may be enumerated as follows: 



STEAM ENGINES 



1G5 



The lubricant must be sufficiently fluid, so that it will not in 
itself make the bearing run hard. 

It must not be too fluid or it will be squeezed out from between 
the bearing surfaces. If this happens, the bearing will immediately 
heat and begin to cut. The heating will tighten the bearing and 
increase the pressure and the cutting. 

It must not gum or dry when exposed to the air. 

It must not be easily decomposed by the heat generated. If it 
should be decomposed, it might form substances which would be 
injurious to the bearings. 

It must not take fire easily. 

It must contain no acid and should form no acid in decomposing, 
as acids corrode the bearings. 

Both mineral and animal oils are used as 
lubricants. Formerly animal oils were used 
entirely, but they were likely to decompose at 
high temperatures and form acids. It is impor- 
tant in using high pressure steam to have "high 
test oils," that is, oils which will not decompose 
or volatilize at the temperature of the steam. 
It was the difficulty of getting such oils which 
made great trouble when superheated steam was 
first used. Mineral oils will stand high tempera- 
tures very readily, and even if they do decompose, 
they form no acids. 

Common Oilers. Engines are lubricated by 
means of oil cups and wipers placed on the Fig 96 s ^ ardType 
bearings wherever required. They are made in of Simple on Cup 
many forms. Formerly, the oil cup was made with a tube extend- 
ing through the oil. A piece of lamp wick or worsted leads from 
the oil in the cup to the tube. Capillary attraction causes the 
oil to flow continuously and drip down the tube. When not in use, 
the lamp wick should be withdrawn. This type of oil cup is now 
seldom used. 

The oil cup shown in Fig. 96 is simple and economical. The 
opening of the valve is regulated by an adjustable stop. The oil 
may be seen as it flows drop by drop. The cylindrical portion is 
made of glass, so that the operator can see how much oil there is in 
the cup without opening it. 




166 



STEAM ENGINES 




Fig. 97. Form of Wiper Crank Pin Oi 



A form of wiper crank pin oiler is shown in Fig. 97. The oil 
cup is attached to a bracket. The oil drops from the cup into the 

sheet of wicking or wire cloth 
and is removed at each rev- 
olution of the crank pin by 
means of the cup which is 
attached to the end of the 
connecting rod. This form of 
oiler works very satisfactorily 
at slow speeds. 

Centrifugal Oilers. Fig. 98 
shows a centrifugal oiling de- 
vice which operates very sat- 
isfactorily at all speeds. The oil flows from the oil cup through 
the tube to the small hole in the crank pin by centrifugal force. It 

reaches the bearing surface by 
means of another small hole. 

Cylinder Lubrication. In oiling 
the valve chest and the cylinder, 
the lubricant must be introduced 
against the pressure of the steam. 
This may be done in several ways, 
in each of which it is introduced 
into the steam before it reaches 
the valve chest and is carried 
by the steam to the surfaces to 
be lubricated. 

By Oil Pumps. The oil may 
be forced into the steam pipe by 
a small hand pump or, in large 
engines, by an attachment from 
the engine itself. The supply of 
oil is, of course, intermittent if the 
pump is driven by hand, but continuous and economical if driven 
by the engine. 

By Sight-Feed Lubricators. The most common device for feed- 
ing oil to the cylinder is that which introduces the oil drop by drop 
into the steam when it is in the steam pipe or steam chest. The oil 




Fig. 98. Centrifugal Oiler 



STEAM ENGINES 



1G7 



becomes vaporized and lubricates all the internal surfaces of the 
engine. 

Fig. 99 shows the section of a sight-feed lubricator, which must 
be placed on the steam supply pipe in a vertical position above the 
throttle. The reservoir is filled with oil. The pipe B, which 
connects with the steam pipe, is partly filled with condensed steam 
which flows down the small curved pipe E to the bottom of the cham- 
ber 0. A small portion of 
the oil is thus displaced and 
flows from the top of the res- 
ervoir down the tube F 
by tRe regulating valve D, 
and up through the glass 
tube S, which is filled with 
water. It enters the main 
steam pipe through the con- 
nection A. The gauge glass 
G indicates the height of 
water in the chamber 0. To 
fill the lubricator, close the 
regulating valve D and the 
valve in pipe B; the oil 
chamber can thus be drained 
through the cock C, and 
filled. If the glass S be- 
comes clogged, it may be 
cleaned by closing valve D 
and opening the small valve 
//. This will allow the steam to blow through the glass. After 
cleaning close valve // and allow glass S to become filled with 
water before opening the feed valve. The amount of oil fed to 
the cylinder can be regulated by opening the valve D the proper 
amount. The exact quantity of oil necessary for the engine is not 
easily determined. For ordinary sizes it is from one to four drops 
per minute, depending on the conditions. 

Instructions for Proper Lubrication. In slow speed engines it is 
not a difficult matter to attend to the oiling; all the parts are mov- 
ing slowly and can be readily examined and oiled. Many high speed 




Fig. 99. Section of Sight-Feed Lubricator 



168 STEAM ENGINES 

engines run so fast that it is impossible to examine the various parts, 
and special means must be provided for lubrication. It is especially 
important in high speed engines that there should be no heating. 

In order to avoid the danger of neglecting to oil a bearing of a 
high speed engine, it is customary to have all the bearings oiled from 
one central source. All the oil is supplied to one reservoir, from 
which pipes lead to all bearings. If this is not done, large oil cups 
are used, as a rule, so that oiling need not be attended to as frequently. 

In some high speed engines the moving parts are enclosed and 
the crank runs in a bath of oil. This secures certain oiling and is 
very effective. All the bearings may be inside this crank case, so 
that all are oiled in this way. It is thus impossible for a careless 
operator to overlook one point and so endanger the whole engine. 

Starting the Engine. Before starting an engine, the oil cups 
should be started feeding, grease cups screwed down, and the gov- 
ernor and other parts of the valve gear oiled. The cylinder lubri- 
cator should be started before the engine so that the oil passages 
will contain oil. The cylinder drain cocks should be open so that 
any condensed steam in the cylinder will be removed without injury 
to the cylinder. These precautions having been observed, the 
throttle may be opened slowly and the engine started and gradually 
brought to the required speed. 

After starting the engine, notice should be taken of the governor 
and all the lubricating apparatus to see that each is properly per- 
forming its function. 

When the engine is to operate condensing, the condenser should 
be started first, if it is in such a position that the water in the 
exhaust can drain into it. If the condenser is above the engine and 
no means are provided for removing the water, the engine should be 
started non-condensing. When a jet condenser is used, the quan- 
tity of injection water should be increased as the load is increased; 
the amount being determined by the conditions of the vacuum and 
temperature of the discharge water, which should be from 100° to 
110°F. If the water is colder than this, it would denote that more 
injected water is being used than is required. 

The foregoing suggestions and indicated precautions are only 
a few of the more important things that will arise in the course of the 
erection, setting, and operation of an engine. The one performing 



STEAM ENGINES 1H0 

these various duties must at all times exercise good judgment and 
act according to what his past experiences and that of others have 
taught under similar circumstances. 

ENGINE SPECIFICATIONS 

Selecting an Engine. The engineer who has the responsibility 
of selecting an engine for a given class of service has no small task 
to perform, if he carefully analyzes all the factors entering into the 
problem. If the installation contemplated is to be an extensive or 
expensive one, expert advice should be solicited. Since this is not 
always to be had, a few suggestions will be given as to how best to 
proceed when one has to specify an engine for a given service. Con- 
sider for the time being that an expert consulting engineer is not avail- 
able and a rather inexperienced person, or non-technical man, who 
knows little about the theoretical questions that should be given 
consideration, has to select the engine. In this case the most satis- 
factory procedure to follow would be to go to some reliable engine 
builder and ask him to build or specify an engine that would per- 
form the service required. Having only one builder intrusted, the 
item of expense would not be chief in his consideration since there 
would be no competition, therefore the builder would build or specify 
the best engine possible for the service. If the funds available 
are limited or must be closely conserved, the intended purchaser may 
state the limits of cost and then require the builder to come w T ithin 
those limits. It would also be wise on the part of the purchaser 
to require a guarantee as to the performance of the engine and its 
maintenance cost for a given period of one year or more. 

Drawing Up Specifications. If the purchaser is a competent 
engineer or he has in his employ such a person, a complete set of 
specifications may be drawn up and submitted to several engine 
builders for competitive bids. The specifications submitted should 
cover in detail the service for which the engine is to be used, the 
speed at which it is to operate, the type of valves and valve gear 
desired, the per cent of variation permissible in its governing, and 
many other items as to the design and detail of construction. Most 
specifications also specify within what limits the engine must operate, 
as to the amount of steam used per indicated horsepower per hour, 
and the range of mechanical efficiency that must be attained. A pro- 



170 , STEAM ENGINES 

vision should be made in the contract as to the conditions under 
which the acceptance test will be made and by whom. 

The form of specification usually submitted by the builders 
and which in general will be like those written by an engineer when 
requesting bids, is submitted herewith. This may be taken as a 
typical specification, the items being changed to meet different con- 
ditions of service as the particular case demands. 



SPECIFICATIONS OF A VERTICAL CROSS-COMPOUND, SIDE- 
CRANK, ENGINE, ARRANGED FOR 1000-K.W. DIRECT 
CONNECTED GENERATOR, 60 CYCLE ALTERNATOR 

Size, Power, and Dimensions 

Diameter of high pressure cylinder, 27 inches. 

Diameter of low pressure cylinder, 54 inches. 

Stroke, 42 inches. 

Revolutions per minute, 120. 

Initial steam pressure, 125 pounds, 26 inches vacuum, condensing. 

Rated load in indicated horsepower, 1,520; cut-off, 26/100. 

At % cut-off, indicated horsepower, 2,100; maximum cut-off, 7/ 10. 

Estimated total weight of engine, 346,000 pounds. 

Weight of wheel, 92,000 pounds. Diameter, 16 feet. Face, inches. 

Diameter of bearings, 19 inches. Length, 35 inches. 
Diameter of shaft between bearings, 22 inches. 
Diameter of crank pin, 9 inches. Length, 8 inches. 
Diameter of crosshead pin, 8 inches. Length, 8 inches. 
Bearing surface of crosshead, 17 inches by 20 inches. 
Diameter of piston rod, 5 inches. 
Diameter of throttle valve, 12 inches. 
Diameter of exhaust opening, 22 inches. 

Workmanship and Materials 

The workmanship, finish, fitting, and materials will be first-class in every 
particular. All forgings will be of open-hearth steel or hammered iron, as 
hereafter specified. All castings subject to wear, such as cylinders, guides, 
pistons, etc., will be poured from mixtures containing charcoal iron, graded 
according to the size of casting in order to secure the proper hardness and 
closeness of grain. 

The engine will be made to gauge and interchangeable. This feature 
will be thoroughly carried out. 

Flat surfaces will be scraped to surface plates, and surface and cylindri- 
cal grinding will be used where advantageous. 

Guarantee 

We guarantee the workmanship and materials in the engine to be first- 
class and in fulfillment of our guarantee we will give a duplicate to take the 
place of any part that may prove defective in material, workmanship, or 
design within one year after the engine is started. 



STEAM ENGINES 171 

We guarantee the engine to regulate from no load to full rated load within 
2 per cent variation of speed. 

We guarantee the engine to run in a smooth and proper manner with- 
out undue heating or vibration. 
Cylinders 

The cylinders and steam chests will be neatly covered with sheet iron 
lagging, enclosing a thick layer of the best quality of asbestos or magnesia 
fiber. The cylinder and steam chest covers will also be provided at each end 
with thin iron castings or covers. The cylinders will be provided at each 
end with a patent combination relief-valve and drip-cock of large diameter, 
adjustable to open automatically at any pressure desired. Being operated 
by hand as drip-cocks, these will not stick or become inoperative from dis- 
use, but will relieve dangerous pressure from water or other causes. 
Jackets and Receiver 

The high pressure cylinder will be steam-jacketed and there will be a 
receiver of large capacity between cylinders. 

The receiver will be filled with seamless brass heating coils containing 
steam at boiler pressure. The high pressure jacket and these coils should 
be piped in series, so that steam will pass through in the order named, and 
since the steam in the low r pressure coils is hotter than the receiver steam, 
the latter w T ill be considerably superheated upon entering the low pressure 
cylinder, and enough of the former will be condensed in the coils to cause 
brisk circulation in the high pressure cylinder jacket which is necessary 
to its efficiency. It is the aim of this arrangement to keep the steam dry 
throughout its course through the engine without the loss of any portion of 
heat of the jacket to the exhaust steam. The water condensed in jackets 
and in the coils should be returned to the boiler. 
Valves 

Both cylinders will be four-ported and provided with valves of the flat 
gridiron type of our standard form. 

The valves slide crosswise of the cylinder upon gridiron seats, which are 
separate and removable from the cylinder itself. Since the valves are of 
the gridiron type, a very small stroke is necessary to give full opening, and 
they move with an intermittent motion, standing still when closed, and only 
require power to operate when open and relieved of steam pressure. The 
clearance is reduced to about one-half of that necessary with valves of the 
Corliss type. 

These valves possess the following advantages: 

They give rapid opening of port with the least amount of wear and 
power required to operate. 

The clearance space is reduced to a minimum. 

They will not stick when the engine is started, and are easy to keep 
lubricated. 

They wipe over and wear evenly, are unbalanced, and hence will be 
tight when old as well as w r hen new. 

Valve Gear 

The main valves will be driven by a fixed eccentric controlling the admis- 
sion of the steam and the opening and the closing of the exhaust. The cut- 
ting off of the steam will be effected by the cut-off valves which are con- 
trolled by the governor. 



172 STEAM ENGINES 

The valve gear is positive, composed of simple levers and links, and the 
cut-off can take place at any point between zero and the maximum cut-off. 
The cut-off, except at light loads, occurs when the main and cut-off valves 
are moving in opposite directions, and the cut-off is as sharp as with a releas- 
ing type of valve gear notwithstanding the short stroke used. 

The cut-off is varied simultaneously upon all the cylinders in such a man- 
ner that the work done in each is approximately equal, as is also the drop 
in temperature of steam in each. This adds to smooth running and gives 
best distribution of steam for economy at all cut-offs under variable loads. 

The valve gear will be constructed in the most substantial and durable 
manner, and in such a way as to equalize the cut-off at both ends of the cylin- 
ders for all cut-offs. Rock-shafts, pins, and links will be made of open- 
hearth steel. Connecting links will be fitted with bronze ends having quick 
taper key adjustment. The eccentric straps will be lined with babbitt 
hammered in and bored out. The rock-shaft bearing will be babbitted 
and adjustable. 
Governors 

The governor will be situated on the main shaft of the engine. A change 
in position of the centrifugal weights revolves the eccentric controlling the 
position and motion of the cut-off valves around the shaft and varies the 
point of cut-off. 

All the bearing pins in the governor will be made of tool steel hardened 
and ground, turning in bearings bushed with phosphor bronze. The cen- 
trifugal force of each governor weight is resisted by a plate spring through 
a pin having hardened steel points resting in phosphor bronze cups, one at 
the end of the spring and the other at the center of gravity of the governor 
weight. The centrifugal force of the governor weights is thus opposed in a 
direct and frictionless manner without causing pressure or friction on the 
pins upon which the governor weights swing. This governor will regulate 
the speed of the engine with a closeness and certainty impossible with a 
fly-ball governor, and its action is unaffected by wide and sudden fluctua- 
tions of load. The governor will control both cut-off eccentrics. 
Pistons, Piston Rods, and Stuffing Boxes 

The pistons will be cored out and provided with internal ribbing, mak- 
ing them very light and strong. They will be secured to the piston rod by 
being forced upon a taper, with shoulder beyond, and by a nut, with a simple 
but efficient locking device. The pistons will be provided with cast-iron 
packing rings. 

The piston rods will be of open-hearth steel running through deep stuff- 
ing boxes and babbitted glands. The rods will not touch the heads — which 
will be bored large — bronze rings fitting the rods in the bottom of each 
stuffing box and preventing escape of packing to the interior of the cylinder. 

Low pressure piston will be of steel. 
Framing 

This will consist, for each cylinder, of a deep and massive base contain- 
ing the main bearings. On the back of each base will stand a very heavy 
rectangular column, as shown in the blue print, securely bolted to a heavy 
frame head. In front the frame heads will be connected to the bases by 
forged steel columns bolted by flanges forged solid with the columns. The 



STEAM ENGINES 173 

rear column will support the cylinders when the forged columns in front 
are removed, facilitating the placing of shaft and other parts. 
Guides, Crossheads, and Crosshead Pins 

The guides will be separate from the frame and adjustable for wear with 
an oil dish at the bottom which, together with a thin brass fringe upon the 
bottom of the crosshead, forms an efficient self-oiling device. 

The crossheads will be of open-hearth steel fitted with babbitted cast- 
iron shoes. 

The crosshead pins will be of open-hearth steel flattened on two sides to 
prevent wearing oval. 
Connecting Rods and Boxes 

The connecting rod will be of forged steel, provided with gib and key 
ends. The straps will be provided with pinching bolts which will prevent 
spreading. Both crank and crosshead pin boxes will be lined with babbitt 
hammered in and bored out. 

The body of the connecting rod will be made of larger section than the 
piston rod, being designed properly for the added strain due to its length 
and angular motion. 
Shaft, Crank Pin, and Disk 

The shaft will be piled and faggoted hammered iron forging. 

The crank disk will be made with counterbalance, of a mixture contain- 
ing charcoal iron. The crank pin will be made of forged steel. The shaft 
and crank pin will be forced into the disk by hydraulic pressure and the disk 
will also be keyed securely to the shaft. 
Main Bearings and Removable Shells 

The main bearings will be fitted with cylindrical shells, lined with babbitt, 
hammered in and bored out. These shells can easily be taken out by remov- 
ing the cap and simply jacking up the shaft sufficiently to take the weight 
off the bearings, when they can be revolved around the shaft and taken out 
without disturbing any other parts of the engine. The shells are made hol- 
low for water circulation. This is not intended to be used ordinarily, but 
in case dirt or other unusual conditions should cause the bearing to heat, it 
often enables the engine to complete its run without stopping. 

The main bearings will be provided with a self-oiling device which will 
keep them flooded with oil. 
Oil Feed System 

The feed will be positive and adjustable and the system will be closed, 
so that there will be little waste and deterioration of oil. Rings at the ends 
of the bearings will throw off escaping oil into close-fitting shields with suit- 
able drain pipes leading to a large settling reservoir beneath. A small pump 
driven from the valve gear will deliver the oil to a feed tank at each bear- 
ing. This tank will be provided with an adjustable feed outlet pipe leading 
to the bearings, and with a gauge-glass and by-pass overflow, and can be 
filled by hand and used as an ordinary oil cup if it is desired to cut off the 
automatic supply while the engine is running. 
Flywheel 

The wheel will be cast in halves and will be bolted together at the hub 
with reamed bolts carefully fitted in holes drilled from the solid, and the 
parts will be planed where they join. Steel arrow head links will be used 



174 STEAM ENGINES 

at the rim. The wheel will be carefully designed throughout in order to 
have a large factor of safety, and both edges and face of rim will be turned 
true. 

Platforms 

Platforms convenient for handling and operating the engine will be pro- 
vided as shown in print. These can be arranged to suit the location of the 
engine and will be made stiff to avoid vibration. The hand railings will be 
of seamless brass tubing, fitted into brass caps or iron posts. The platform 
plates will be diamond figured, planed where they join together and neatly 
fitted. Stairs will be made of channel iron, with cast-iron diamond threads. 

Fixtures 

The following fixtures will be provided: throttle valve; indicator motion; 
complete outfit of sight-feed cylinder lubricators; glass body oil pumps; 
grease cups for valve gear; centrifugal crank pin oilers; reservoirs with sight- 
feed outlets; oil pipes and wipers for oiling the main parts of the engine con- 
veniently and continuous^; relief valves for each end of the cylinders; drip- 
cocks; wrenches, foundation bolts; and foundation plans. 

Contract. After the engine has been selected and the builders 
determined, a written contract should be entered into in order to 
make it a legal document. A contract, according to Blackstone, is 
an agreement upon sufficient consideration to do or not to do a par- 
ticular thing. In the case of the purchasing of an engine, the builder 
agrees to build, erect, and put into operation an engine in accord- 
ance with the specifications and drawings submitted, which items 
become a legal portion of the contract. The purchaser may also 
require that the engine be ready for operation in a given time and 
that it must also come up to certain requirements in its performance, 
as previously mentioned. In consideration of the foregoing, the 
purchaser agrees to pay the builders a specified sum of money, either 
in one payment or more as determined by them. The wording and 
statement of the contract should be carefully prepared, in order to 
avoid any possible misinterpretation of any of its provisions. 

COST OF ENGINES AND OF THEIR OPERATION 

The question of the cost of an engine and of its erection and 
operation is indeed a very vital one. This cost can not be classified 
in a brief way, since there are so many contributing factors that differ 
widely in different localities. For example, no well-defined indica- 
tion of the cost of operation can be given, and the cost of labor 
and material are fluctuating items of expense; therefore, the cost of 
the engine can not be stated definitely, since in a brief interval of 
time it may be considerably more or less. Many articles appear 



STEAM ENGINES 



175 



TABLB III 
Price of Single Cylinder Corliss Engines, Set and Erected 



Size of 


Horse- 


Cost of 


Cost of 


Cost of 


Cost of 


Total Cost 


Cylinder, Inches 


power 


Engine 


Foundation 


Erecting 


Piping 


16X36 


125 


$1950 


$325 


$210 


$180 


$2665 


18X36 


155 


2150 


375 


240 


200 


2965 


18X48 


200 


2600 


425 


260 


220 


3505 


20X48 


230 


2850 


525 


275 


250 


3900 


22X42 


250 


3000 


550 


300 


310 


4160 


24X48 


320 


4000 


700 


375 


390 


5465 


28X48 


425 


5150 


900 


500 


800 


7650 


30X48 


490 


5800 


1200 


600 


1070 


8670 



from time to time in the leading engineering papers which give val- 
uable information upon such matters and usually this information 
is correct since it is given currently with the ascertained cost of 
various items. It is, therefore, suggested that if the latest and per- 
haps most authentic information is desired upon these items of 
expense that such articles as appear in the papers mentioned should 
be consulted. 

Engine Costs. As an indication of what such expense will be 
Tables III and IV, as devised by Dean C. H. Benjamin, are given. 



TABLE IV 

Cost of High Speed, Single Cylinder Engines 



o 

ft 
Oi 
<n 
>_ 
O 
tfl 


Size of 

Cylinders 

Inches 


OQ 




6* 


3 
CO u 

o 
O 


a 

c c a 


a|| 

CO § 


us 

° 5 


2 11 

*.S 3 

o mo 


50 


9X10 


100 


300 


$695 


$45 


$65 


$70 


$10 


$885 


75 


10X12 


100 


300 


890 


50 


75 


70 


15 


1100 


100 


12 X 12 


100 


290 


1085 


50 


80 


70 


15 


1300 


125 


13X14 


100 


275 


1260 


70 


95 


70 


17 


1512 


150 


15X14 
14X16 


100 


245 


1595 


80 


110 


75 


20 


1880 


200 


18X16 


100 


225 


2010 


90 


140 


85 


25 


2350 


250 


19X18 


100 


200 


2800 


250 


200 


100 


35 


3385 



Relative Cost of Operation Items. The cost of the operation 
of a steam plant is properly made up of several items, viz, rent or 



176 STEAM ENGINES 

TABLE V 
Cost of Installation and Operation for One Year 



Kind of Engine 


O «3 02 

eS.S'o 


Annual Cost 
of Both Engine 
and Boilers, 
Depreciation 
and Interest 


I- 03 
03 =3 *J 

O o 


a 
a 
o 

3 
h3 


"0 

oj.S o 

G 

w 


Cost of Power, 

Coal at $2 Per 

Ton, 1 Year 

1 


Simple Slide Valve Non-con-1 
densing J 


$29.75 


$4.03 


6750 


$1.02 


$5.00 


$23 . 55 


Compound Slide Valve Non-1 
condensing J 


31.50 


4.38 


5660 


1.25 


4.50 


21.45 


Compound Slide Valve Condens-1 
ing J 
Simple Corliss Non-condensing 


29.80 
32.25 


4.26 
3.84 


4050 
6075 


1.25 
1.00 


3.80 
4.70 


17.41 
21.00 


Compound Corliss Condensing 


30.87 


3.76 


3375 


1.25 


3.50 


16.25 


Triple Corliss Condensing 


34.25 


4.28 


3110 


1.50 


4.00 


16.00 



interest on real estate; interest on investment; maintenance, etc., 
of equipment; fuel; water; supplies; and attendance. 

The relative value of these various items for a large central sta- 
tion lighting plant was given in the Engineering Magazine, May, 
1905. Taking the total cost of maintaining the station as 100 per 
cent, the following were the average costs of the various items: 
Fuel 52.5%; wages 26.4%; water 2.2%; oil and waste 1.8%; rent 
4.35%; station repairs 2.2%; steam repairs 5.45%; electric repairs 
5.1%. 

Annual Operation Expenses. Professor Carpenter in the 
Economist summarizes the cost of installation and the operation of 
an entire plant for one year of 3,000 hours as given in Table V. 
A coal consumption of 4.5 pounds per boiler horsepower per hour is 
assumed and the cost given per engine horsepower is for a 1,000 horse- 
power engine. 

An illustration involving the items given in Table V will serve 

to make it clearer. The case of a simple slide valve non-condensing 

plant will be considered. 

Cost of engines and boilers at $29.75 per horsepower = $29,750. 
Annual cost of depreciation and interest at $4.03 per h.p. =$4,030. 
Annual cost of coal at $2.00 per ton =6750X2 =$13,500. 
Annual cost of lubricants at $1.02 per horsepower = $1.02X100 = $1,020. 
Annual cost of labor at $5.00 per horsepower = $5.00X1000 = $5,000. 

Annual cost for the last four items = $23,550 or $23.55 per h.p. 



STEAM ENGINES 177 

The foregoing tables will serve to give some idea of the cost of 
engines, also of the cost of operation of a steam plant, but it must be 
remembered that the figures given will not be exact for all localities 
or for all times, due to the changing influences previously mentioned. 

ENGINE TESTS 

Importance of Tests. It was mentioned in connection with the 
discussion of specifications and contracts that often a guarantee is 
given by the builder as to the economical performance of a steam 
engine, hence it is required that the engine be tested in order to ascer- 
tain whether or not it meets the provisions of the guarantee. While 
this is one reason that may be assigned for testing an engine, yet 
there are several others of importance. The user from time to time 
may want to ascertain the condition of the engine as a whole and 
also the condition of particular features such as the valves, etc. For 
purely theoretical reasons an engine is often tested in order that 
an analytical study may be made of its performance under various 
conditions and in comi orison with other engines of different classes. 
Many such tests have resulted in obtaining data, the facts of which 
have demonstrated to both the builder and the user possible econo- 
mies. Because of the information thus obtained, the builder has 
been enabled to design a better engine, and the user to operate his 
engine more advantageously. The remarks given will suffice to 
indicate that the ultimate object of an engine test is the determina- 
tion of the economy with which the engine produces a given amount 
of potver. In steam engines the economy, as usually ascertained, 
relates to the weight of steam consumed, to the quantity of coal 
required to make the steam, or to the number of heat units supplied. 
The elementary quantities concerned are accordingly two in num- 
ber, viz, the amount of steam, fuel, or heat (as the case may be) 
consumed, and the amount of power developed. How to determine 
these quantities is the problem. 

A. S. M. E. Code. The American Society of Mechanical 
Engineers (A.S.M.E.) deemed the testing of engines according to 
some definite and standard method of such importance that a com- 
mittee was appointed to devise a standard code. This, after much 
labor and diligent study, was presented to the Society and adopted. 
The full report appears in Volume 24 (1904), page 713, of the Trans- 



178 STEAM ENGINES 

actions. This code indicates the method of obtaining the required 
data and also gives a recommended form of report. In so far as the 
conditions will permit, this code should be followed. The several 
items of the code are summarized as follows: 

Method of Conducting Steam Engine Tests — Code of 1902 

(1) Object of Test. Ascertain at the outset the specific object 
of the test, whether it is to determine the fulfillment of a contract 
guarantee, to ascertain the highest economy obtainable, to ascertain 
the performance under special conditions, to determine the effect of 
changes in the conditions, or to find the performance of the entire 
boiler and engine plant, and prepare for the test accordingly. 

No specific rules can be given for the preparations for the test 
as conditions surrounding each test will require a more or less differ- 
ent solution, which must be solved by the one in charge. The one 
particular thing to be emphasized at all times is, that in order to 
obtain data that is absolutely reliable for the purpose in view, the 
one in charge must be vigilant, conscientious, and, above all, 
honest. 

(2) General Condition of the Plant. Examine the engine and 
the entire plant concerned in the test; note its general condition and 
any points of design, construction, or operation which bear on the 
objects in view. Make a special examination of the valve and pis- 
tons for leakage by applying the working pressure with the engine 
at rest and observe the quantity of steam, if any, blowing through 
per hour. 

If the test is for the purpose of ascertaining the highest efficiency, 
the valves and pistons must be made steam- and water-tight. 

To test the valves and piston block the flywheel so the piston 
will be near one end of the stroke, and turn on the steam. The leak- 
age will escape to the exhaust port and will be observable. Another 
approximate method is to block the engine as before and having an 
indicator on the cylinder, observe the drop in pressure after an inter- 
val of time. In a tight engine the fall of pressure will be slow, 
whereas in a leaky one it will be fast. Other methods of determining 
the amount of leakage may suggest themselves to the engineer in 
charge of the test. 

(3) Dimensions, etc. Measure or check the dimensions of the 
cylinders in every case, this being done when they are hot. If they 
are much worn, the average diameter should be determined. Meas- 
ure also the clearance, which should be done, if possible, as described 



STEAM ENGINES 179 

in "Valve Gears." If the clearance can not be determined directly, 
it can be done approximately from the working drawings of the 
cylinder. 

(4) Coal. When the trial involves the complete plant, embrac- 
ing boilers as well as engine, determine the character of the coal to 
be used. The class, name of the mine, size, moisture, and quality 
of the coal should be stated in thfe report. 

(5) Calibration. All instruments and apparatus should be 
calibrated and their reliability and accuracy verified by comparison 
with recognized standards. Such apparatus which is liable to 
change or become broken during the test, as gauges, indicator springs, 
and thermometers, should be calibrated before and after the test. 
The accuracy of scales should be verified by standard weights. Any 
water meters used should be carefully calibrated before and after, 
and during the test if possible. All of the apparatus may be very 
easily tested, directions for which may be found in various hand- 
books of engineering and often in instruction pamphlets published 
by the manufacturers. The method of testing indicator springs is 
given in "Steam Engine Indicators." 

(6) Precaution. Make sure that there is no leakage at any of 
the connections with the apparatus provided for measuring and sup- 
plying the feed water and the steam that could affect the results. 

(7) Duration of Test. The duration of a test should depend 
largely upon its character and the objects in view. The standard 
test of an engine and, likewise, a test for the simple determination 
of the feed water consumption should be continued for at least five 
hours, unless the class of service prevents a continuous run of so long 
duration. 

When the water discharged from the surface condenser is meas- 
ured for successive short intervals of time, and the rate is found to be 
uniform, the test may be of much shorter duration than when the 
feed water is measured to the boiler. The longer the test with a 
given set of conditions, the more accurate the work. 

The commercial test of a complete plant, embracing boilers as 
well as engines, should continue at least one full day of twenty-four 
hours, whether the engine is in motion the entire time or not. A con- 
tinuous coal test of a boiler and engine should be at least of ten 
hours duration, or the nearest multiple of the interval between 
times of cleaning fires. 

(8) Starting and Stopping a Test. Before beginning to take 
readings the engine should be operated a sufficient length of time for 



180 STEAM ENGINES 

it to become thoroughly heated in all of its parts, and in the mean- 
time all of the measuring apparatus should be properly adjusted. 
Having made the preliminary arrangements mentioned, at a given 
signal the height of water in the gauge glasses of boilers is observed, 
the depth of water in the reservoir from which the feed water is 
supplied is noted, the exact time of day is observed, and the test is 
held to commence. Thereafter the measurements determined upon 
for the test are begun and carried forward until its close. It is con- 
venient to begin the test at some even hour or minute, but the impor- 
tant thing is to begin the test when accurate readings can be obtained 
irrespective of the time. When the time for closing the test arrives, 
the water in the glasses should be brought to the same height as it 
was at the beginning; if this is not possible, corrections must be made 
in the report. 

(9) Measurements of Heat Units Consumed by the Engine. The 
measurement of the heat consumed requires the measurement of all 
the water supplied to the boiler, by whatever means; the tempera- 
ture of the water supplied from each source; together with the pres- 
sure and quality of the steam, which are to be taken at some point 
near the throttle valve. The quantity ol steam used by the steam 
calorimeter must also be accounted for. 

The heat to be determined is that used by the entire engine 
equipment, embracing the cylinders and all auxiliary cylinders and 
mechanisms concerned in the operation of the engine, including air 
pumps, feed pumps, reheaters, etc. 

(10) Measurement of Feed Water, or Steam Consumption of 
Engine, etc. The method of determining the steam consumption 
applicable to all plants is to measure all the feed water supplied to 
the boilers and deduct therefrom the water discharged by separa- 
tors and drips, as also the water and steam which escapes on account 
of leakage of the boiler and its pipe connections and leakage of the 
main and branches connecting the boiler and engine. In plants 
where the engine exhausts into a surface condenser the steam con- 
sumption can be measured by determining the quantity of water 
discharged by the air pump, corrected for any leakage of the con- 
denser and adding this to the steam used by jackets, reheaters, and 
auxiliaries as determined independently. 

In measuring the water it is best to carry it through a tank or 
tanks resting upon platform weighing scales suitably arranged for 
the purpose, the water being afterwards emptied into a reservoir 
beneath, from which the pump is supplied. 



STEAM ENGINES 181 

(11) Measurement of Steam Used by Auxiliaries. Although the 
steam used by the auxiliaries was measured as mentioned in item (10), 
yet it is very desirable to ascertain the steam consumption of each 
auxiliary independently, in order that a close analysis of the engine 
performance can be made. Several means may be employed for 
determining the steam consumption of the various auxiliaries, and 
since they will be apparent to the operator no discussion of them 
will be given, but they are only mentioned in order to emphasize the 
desirability of obtaining such data. 

(12) Coal Measurement. In commercial tests of the combined 
engine and boiler equipment, or those made under ordinary condi- 
tions of commercial service, the test should extend over the entire 
period of the day, that is, twenty-four hours, or a number of days 
of that duration. Consequently, the coal consumption should be 
determined for the entire time. If the engine runs but a part of the 
time and during the remaining portions the fire is banked, the meas- 
urement of coal should include that used for banking. It is well, 
however, in such cases to determine separately the amount consumed 
during the time the engine is in operation and that consumed dur- 
ing the period while the fires are banked, so as to have complete 
data for purposes of analysis and comparison, using suitable precau- 
tions to obtain reliable measurements. The measurement of coal 
begins with the first firing, after cleaning the furnaces and burning 
down at the beginning of the test, and ends with the last firing, at the 
expiration of the allotted time. 

In connection with coal measurements, whatever the class of 
tests, it is important to ascertain the percentage of moisture in the 
coal, the weight of ashes and refuse, and, where possible, the approxi- 
mate and ultimate analysis of the coal. (For discussion of this item 
of coal the student is referred to Vol. 22, P. 34, of the A. S. M. E. 
Transactions.) 

(13) Indicated Horsepower. The indicated horsepower should 
be determined from the average mean effective pressure of diagrams 
taken at intervals of twenty minutes, and at more frequent intervals 
if the nature of the test makes this necessary for each end of each 
cylinder. 

The indicator diagrams should be taken at regular intervals 
but not necessarily simultaneously at the two ends of the cylinder. 
If the diagrams vary so much as not to give fair results, the diagrams 
should be taken more frequently. 

The method of attaching, operating, and adjusting the indicator 



182 STEAM ENGINES 

and also the method to follow in obtaining the mean effective pres- 
sure are described in ''Steam Engine Indicators." 

(14) and (15) Testing Indicator Springs and Brake Horsepoiver. 
These items are fully discussed and explained in "Steam Engine 
Indicators." 

(16) Quality of Steam. When ordinary saturated steam is used, 
its quality should be obtained by the use of a throttling calorimeter 
attached to the main steam pipe near the throttle valve. When the 
steam is superheated, the amount of superheating should be found 
by the use of a thermometer placed in a mercury well inserted in the 
pipe. 

(17) Speed. There are several means for obtaining the num- 
ber of revolutions the engine makes per minute. They may be 
counted during one minute or some other division of time, a tach- 
ometer may be used, but the most reliable results are obtained by 
using a revolution counter, such as was illustrated and described in 
"Steam Engine Indicators." In using the counter, the total reading 
should be taken each time the general test data is recorded. These 
revolutions per minute corresponding to the difference in reading of 
the instrument can then be computed, knowing the time interval. 

(18) Recording Data. Take note of every event connected with 
the progress of the trial, whether it seems at the time to be impor- 
tant or unimportant. Record the time of every event, and time of 
taking every weight, and every observation. Observe the pressures, 
temperatures, water heights, speeds, etc., every twenty or thirty 
minutes when the conditions are practically uniform, and at much 
more frequent intervals if the conditions vary. Observations which 
concern the feed water measurements should be made with special 
care at the expiration of each hour of the trial, so as to divide the 
tests into hourly periods and show the uniformity of the conditions 
and tests as the test goes forward. Where the water discharged 
from the surface condenser is weighed, it may be advisable to divide 
the test by these means into periods of less than one hour. 

The data and observations of the test should be kept on properly 
prepared blanks or in notebooks containing columns suitably arranged 
for a clear record. 

(19) Uniformity of Conditions. In a test having for an object 
the determination of the maximum economy obtainable from an 
engine, or where it is desired to ascertain with special accuracy the 
effect of predetermined conditions of operation, it is important that 
all the conditions under which the engine is operated should be main- 



STEAM ENGINES 183 

tained uniformly constant. This requirement applies especially to 
the pressure, the speed, the load, the rate of feeding, the various sup- 
plies of water, the height of the water in the gauge glasses, and the 
depth of the water in the feed water reservoir. 

(20) Analysis of Indicator Diagrams, (a) Steam accounted for 
by the indicator. The method of accounting for the steam by use 
of the indicator is thoroughly treated in "Steam Engine Indicators," 
so no further discussion will be given here, (b) Sample indicator 
diagrams. In order that the report of a test may afford complete 
information regarding the conditions of the test, sample indicator 
diagrams should be selected from those taken and copies appended 
to the tables of results. 

The points at which the different events occur should be clearly 
marked on the cards submitted with the report. 

(21) Standards of Economy and Efficiency. The hourly consump- 
tion of heat determined by employing the actual temperature of the 
feed water to the boiler, as pointed out in item (9), divided by the 
indicated and brake horsepower, that is, the number of heat units 
consumed per indicated or brake horsepower per hour — these are the 
standards of engine efficiency recommended. 

It is useful in this connection to express the efficiency in its more 
scientific form, or what is called the "thermal efficiency ratio." The 
thermal efficiency ratio is the proportion which the heat equivalent 
of the power developed bears to the total amount of heat actually 
consumed, as determined by test. The heat converted into work 
represented by one horsepower is 1,980,000 foot pounds per hour, 
and this divided by 778 equals 2,545 British Thermal Units. Con- 
sequently the thermal efficiency ratio is expressed by the fraction 

2545 \ 

British Thermal Units per hour 

{22, 23, 24, and 25). These sections of the Code deal with purely 
scientific investigations, hence they do not essentially enter into com- 
mercial tests and will not be given. 

(26) Report of Test. The data and results of the test should be 
reported in the manner and in the order outlined in the following 
report. It is the intention that the report be full enough to apply 
to any type of engine, but when not so, or where special data and 
results are determined, additional results may be inserted under the 
appropriate headings. 

Actual Engine Test. To illustrate the application of many of 
the items given as obtained from the Code, a full engine test will be 



184 



STEAM ENGINES 



taken and reported upon. This report will serve to give the order 
and manner in which data should be tabulated and also the method 
in which the report should be worked up. 



DETERMINATION OF EFFICIENCY OF A BUCKEYE ENGINE 
UNDER DIFFERENT LOADS 

Purpose 

The purpose of this series of tests on the Buckeye engine located in the 
Engineering Laboratory of Purdue University was to determine the best 
efficiency under six different loads, ranging from zero to 1$ load, by \ load 
steps, the engine running non-condensing and using 160 pounds of steam pres- 
sure, absolute. 

Plan 

The zero load was determined with the friction brake /, Fig. 100, removed 
and the engine running free. The full load was determined by the brake load 




Fig. 100. Buckeye Engine Fitted with Prony Brake and Indicators 



which the engine carried with 25 per cent cut-off, this being the builders' rating 
for this type of engine. The \, -|, f, 1, and \\ loads were taken as 25%, 50%, 
75%, 100%, and 125%, respectively, of the full load. 

Steam pressure was maintained constant at the pressure indicated for 
the test. Each test was of one hour duration, the engine having been run 
under conditions of the test a length of time sufficient to permit the condi- 
tions to become constant. 



STEAM ENGINES 185 

Method of Conducting Test 

Constant steam pressure was obtained by throttling the 5-inch steam 
line leading to the engine by means of the pipe line valve. This throttling 
action was not sufficient to cause the steam to become superheated. 

The revolutions per minute were obtained by means of a revolution 
counter. 

Indicator diagrams were taken every five minutes, 13 sets of diagrams 
being obtained for each hour's run. 

Barometer readings were taken every 15 minutes. 

The amount of water was determined by condensing the exhaust steam 
at atmospheric pressure. 

Preliminary Work 

Before commencing the work the engine was placed in as good condition 
as was possible. The governor was adjusted in order to reduce friction; play 
was taken up in the valve gear and the valves were carefully set to give equal 
cut-off on both ends at full load; all stuffing boxes were repacked; the brake 
wheel was turned up and brake recalibrated. 

■?; The pressure in the engine supply line was obtained by tapping a j-inch 
pipe into the main, about 3 feet from the valve. This ^-inch pipe was con- 
nected to a large steam gauge which faced the operator of the throttling valve, 
thus enabling him to watch the gauge all the time and maintain a constant 
pressure. 

Observed Data 

In each test the following observations were taken: 
Steam pressure, constant throughout 
Brake load 

Revolutions per minute 
Weight of condensed steam 
Barometer 
Indicator diagrams 

Results 

Having the above data it becomes possible to calculate the following: 

(1) Per cent of cut-off, head end and crank end. 

(2) Mean effective pressure (m.e.p.), head end and crank end. 

(3) Indicated horsepower, head end and crank end and total. 

(4) Brake horsepower (b.h.p.). 

(5) Friction horsepower (f.h.p.). 

(6) Mechanical efficiency. 

(7) Pounds steam, per indicated horsepower per hour and per brake horse- 
power per hour. 

(8) British Thermal Units per hour, per indicated horsepower and brake horse- 
power per hour. 

(9) Thermal efficiency. 

Constants and Formulas. The constants of the engine and formulas 
employed in obtaining the calculated items in the summary of results, are as 
follows: 



186 



STEAM ENGINES 




Eh § 

5 c 

en 
.2 u 



§5 































§ 






























pAc. 




























1 










1 1 
























































11 
















t 


\ 


15- 














•^ 


Ijy 


















\ 


^ 






<^x 












J 




























• » 


* 
























^^*< 


^ 


^n 




<0 


§ 


"0 





,9 




3 








3 


^ 

8 



















5 


u 


* 


Ac 


7N3I 




7<* 



_ 



STEAM ENGINES 



187 



Diameter of cylinder, 7.75 inches. 
Piston rod diameter, 1.437 inches. 

H.E. area, 47.173 square inches; c.e. area, 45.55 square inches. 
Radius of brake arm, 38.25 inches, equals 3.185 feet. 
Clearance, head end 6.15%; crank end, 6.765%. 
Normal speed, 220 revolutions per minute. 
Heat value of 1 horsepower, 42.42 British Thermal Units. 
Heat value of 1 pound of steam, above 32°F. for 160 pounds absolute. 
1,192.8 British Thermal Units. 

Gauge pressure 15 pounds (approximate) less than absolute pressure. 
The horsepower constants are as follows: 
H.E.-i.h.p. Constant = .001787. (See "Steam Engine Indicators.") 
C.E.-i.h.p. Constant = .001726. 
B.H.P. Constant = .00060695. 
Item (3). At observed revolutions per minute (r.p.m.): 
H.E. -i.h.p. = .001787 Xh.e. m.e.p. Xr.p.m. 
C.E. -i.h.p. = .001726 Xce. m.e.p. Xr.p.m. 
Total i.h.p. =h.e. i.h.p. +c.e. i.h.p. 
It often happens that the engine is not 
operated at the desired speed just at the in- 
stant of taking the reading, hence a correction 
must be made if the indicated horsepower is to 
be expressed and recorded for the normal 
speed. Therefore i.h.p. = total i.h.p. X 220 ■*- 
observed r.p.m. 

Item (4). At observed r.p.m. determined 
as follows: 

B.H.P. = .00060695 Xpounds brake load 
Xr.p.m. 

B.H.P. = .0001904 pounds brake load at 

1 foot radius Xr.p.m. 

At 220 r.p.m., corrected b.h.p. =b.h.p. 

X 220 -r observed r.p.m. 

Item (5). At 220 r.p.m., the f.h.p. =total i.h.p -b.h.p. 

Item (6). At 220 r.p.m., the mechanical efficiency = b.h.p. -f- total i.h.p. 

The pounds of steam per hour at 220 r.p.m. = pounds of steam per hour 

at observed r.p.m. X 220 -f- observed r.p.m. The B.T.U. supplied per hour = 

corrected pounds of steam per hour X total British Thermal Units in 1 pound 

steam, at given absolute pressure above 32°F. 

Item (7). The pounds steam per i.h.p. per hour = corrected pounds 

steam per hour divided by corrected i.h.p. 

The pounds of steam per b.h.p. per hour = corrected pounds steam per 

hour divided by corrected b.h.p. 

Item (8). The British Thermal Units per i.h.p per hour = total British 

Thermal Units supplied divided by 160 X corrected i.h.p. 

The British Thermal Units per b.h.p., per hour = total British Thermal 

Units supplied divided by corrected b.h.p. X 160. 

Item (9). The Thermal Efficiency =42.42 British Thermal Units 

divided by British Thermal Units per i.h.p. per hour 



?" 




































$70 


















tf 




















1 
















*<0 


V 
















JO 


\ 


N 


N^ 












20 








*5a 


/tas 








io 







































■5 IO IS to 15 30 3S 

J *cut orr | 



Fig. 



103. Steam Consumption for 
Different Cut-Offs 



188 



STEAM ENGINES 



TABLE VI 
Indicator Diagram Data for Buckeye Engine Test 



Steam Pressure 160 # Abs. 


cyl. 

END 


CARD 
NO. 


NO LOAD 


J% LOAD 


J / 2 LOAD 


%o.o. 


N7.E.P. 


%ao. 


M.E.P. 


%C.O. 


HE.R 


1 


r 


/ 




.000 


J. 5 8 


14.73 


5.00, 


28.41 


z 




.785 


f.32 


13.98 


5.52 


28.17 


3 




.773 


J.05 


Z4./4 


4.98 


28.37 


4 




.259 


/.05 


Z4.73 


4.71 


26.70 


5 




f.040 


f.05 


13.65 


5.00 


26.82 


6 




.000 


J.05 


J 4.45 


4.46 


26.78 


7 




.000 


.79 


Z4./3 


4.47 


26.30 


8 




.52/ 


.79 


13.4/ 


4.7/ 


26./ 8 


9 




.675 


/. 05 


12.90 


4.71 


27.22 


fO 




f.2.95 


/.05 


Z2.63 


4.97 


27.22 


// 




.675 


J.05 


/2.90 


4.7/ 


27.22 


12 




.529 


f.06 


/4.80 


4.73 


26.30 


/3 




.779 


/.06 


12.44 


4.97 


27.22 


AV. 




.5638 


/.073 


13757 


4.841 


27./ 4 


1 




/ 




4.325 


.77 


18.58 


7.41 


36.59 


2 




4.325 


.76 


/850 


7.66 


36.80 


3 




3.805 


.77 


18.62 


7.65 


36.46 


4 




3.560 


.77 


Z8.58 


7.65 


36.20 


5 




4^.055 


.77 


19. 13 


7.65 


36.20 


6 




3.567 


.77 


J 8.92 


7.66 


36.30 


7 




4.340 


.77 


18.43 


7.65 


36.20 


8 




3.805 


.77 


Z8.37 


7.41 


36.30 


9 




3.805 


.76 


17.70 


7.64 


37.63 


10 




3.785 


.76 


1795 


7.41 


37.8/ 


// 




3.805 


.76 


17.95 


7.65 


36.75 


12 




3.560 


.76 


17.75 


7.40 


36.20 


/3 




4.555 


.76 


17.95 


7.69 


37./ 8 


AV. 




3.9445 


.7653 


18.338 


7578 


36.655 



STEAM ENGINES 



189 



TABLE VII 

Indicator Diagram Data for Buckeye Engine Test 





Steam Pressure 


160 # Abs. 




CYL. 
END 


CARD 
NO. 


% load 


FULL LOAD 


7^4 LOAD 


%ao. 


M.E.P. 


%C.O. 


77.E.P. 


%C0. 


M.E.P. 


% 


r 


/ 


Z3.85 


46.70 


24.90 


6 3.25 


33.92 


77.60 


2 


Z3.85 


44.95 


2 4.05 


63.Z5 


35.22 


7 7.60 


3 


Z3.69 


4 4.75 


24.85 


62.85 


35.32 


7 7.80 


4 


Z3.88 


4 4.75 


2 5./ 5 


63.35 


34.90 


7 7.00 


5 


Z4.40 


44.50 


24.52 


64.6 5 


35.4 Z 


76.60 


6 


Z4.2Z 


45.50 


2 5./ 5 


64. Z5 


35.26 


7 7./0 


7 


73.85 


44.65 


24.2/ 


64.20 


34.27 


7 7.55 


8 


Z3.57 


45.15 


25.05 


63.76 


34.87 


7 7.05 


9 


Z3.65 


4 4.90 


25.Z5 


64.90 


36.2Z 


78.95 


ZO 


Z4.Z5 


46. ZO 


2 4.35 


63.35 


34.05 


77.50 


Z / 


Z4.70 


45.40 


24.42 


63.25 


34.07 


7 7.95 


Z2 


Z3.92 


44.40 


2 5./ 5 


64./ 5 


34.80 


7 8.05 


Z3 


/4./Z 


44. Z5 


25.20 


64.50 


34.72 


77.95 


AV. 


Z3.98 


45.073 


24.78 


63.80 


34.84 


77.537 


1 

1 


r 


/ 


Z4.05 


53.Z5 


24.80 


67.85 


3Z.87 


82.05 


2 


Z4.50 


52.80 


24.75 


67.30 


34.25 


82.30 


3 


Z4.05 


52. Z5 


25./0 


68.70 


33.59 


8/. 80 


- 4 


Z4.32 


53.45 


24.05 


67.50 


32.59 


80.80 


5 


Z4.54 


5Z.80 


24.67 


67.50 


33.32 


8/. 3/ 


6 


Z4.Z Z 


53./ 


24.80 


68.35 


32.83 


8/. 30 


7 


Z4.22 


52.55 


24.28 


68.4 


32.83 


80.80 


8 


Z4.54 % 


52.25 


24.6/ 


68.00 


32.83 


8/. 00 


9 


Z4.28 


5Z.80 


24.80 


68.80 


34.25 


8/. 80 


ZO 


Z4.50 


5Z.85 


24.38 


69.06 


32.90 


80.25 


ZZ 


Z4.54 


52.25 


24.6 O 


68.65 


33.07 


80.75 


Z2 


Z4.54 


53.30 


24.58 


68.55 


33.52 


80.00^ 


/ 3 


74.76 


52.Z5 


24.90 


68.50 


32.63 


30.20 




V 


AV. 


74.38 


52.527 


24.59 


68.30 


33.ZZ 


8Z.Z0 



190 



STEAM ENGINES 



TABLE VIII 



Performance of 

Under Different Cut-off's 

Summary 


OBSERVED 




3 


N N "S 


*5 








AV. M.E.P. 


f.H.P. 


5^ 




38 


1% 


N- cq Q-: 


<o K q5 

1ft 








287./ 


29.82 


434.5 




.564 


3.945 


.289 


/.953 


2.242 


/.72 


* 


227.5 


225.5 


29.83 


550,0 


.97 


Z3.76 


Z8.39 


5.45 


7./ 3 


Z2.66 


Z2.35 


£ 


53Z.O 


222.9 


29.8/ 


849.0 


6.2/ 


27/4 


36.66 


/0.82 


/4./0 


24.92 


24.58 


3 4 


8/5.0 


22/. 9 


29.80 


/ 096.0 


/42 


45.07 


52.53 


Z7.86 


20./0 


37.96 


37.62 


/ 


/J 26.0 


2/7.4 


29.78 


/40/.0 


24.6 


63.80 


67.74 


24.80 


25.62 


50.42 


5Z.00 


/% 


J 3 63.0 


209.7 


29.79 


Z6/4.5 


34.0 


77.54 


8/./0 


29.00 


29.30 


58.30 


6/. 20 



HE 




HE 



CE. 



C£ 



/VD LOAD 





HE 



HE. 



CE 



CE. 





HE 



CE M.E 



CE. 





Fig. 74. Indicator Diagrams Taken During Test of Buckeye Engine 



STEAM ENGINES 



191 



TABLE VIII— Continued 



the Buckeye Engine 

Steam Pressures 160 # Abs. 

of Results. 


CALCULATED 


B.H.P. 


I 

K ^ 

K 


si X 


11 


TOTAL B.T.U 

SUPPL/ED 
PEP MO UP 






S 




^ 
^ 

^ 

§£ 
^ 

^ 




ft 


o 





2.35 





332.5 


396600 


Z4/.4 




28/0 







9.75 


9.54 


2.7/ 


77.2 


547.0 


652500 


44.25 


57.4 


879 


//40 


4.82 


2/. 8! 


2/. 5/ 


3.07 


87.5 


837.0 


998350 


34./ 


38.95 


678 


774 


6.29 


34.4/ 


34./ 8 


3.44 


90.8 


/085.0 


/294300 


28.85 


3/. 80 


573 


632 


7.25 


46.55 


47.Z7 


3.88 


92.5 


/4/8.0 


/ 69/ 5 00 


27.8 


30.5 


552.5 


606 


7.68 


54.45 

m 


5707 


4./3 


93.3 


/695.0 


2022O0O 


27.75 


29.7 


55/ 


590 


7.70 



Plotted Results. On curve sheet shown as Fig. 101, are plotted to pounds 
brake load at 1' radius, the i.h.p., b.h.p., f.h.p., and mechanical efficiency. 

On curve sheet shown as Fig. 102, are plotted to horsepower the pounds 
steam per i.h.p. per hour, the pounds steam per b.h.p. per hour, the British 
Thermal Unit per i.h.p. per minute, the British Thermal Unit per b.h.p. per 
minute, and the thermal efficiency. 

On curve sheet shown as Fig. 103, is plotted a curve which shows the 
steam consumption for the different per cents of cut-off. 

Conclusions and Comparisons 

An examination of the curves shows a marked increase in economy of 
the \ load over the \ load; a smaller increase in economy of the f load over 
the \ load; and a still smaller increase in economy of the full load over the 
f load; but the full load and l{ load have the same steam consumption per 
i.h.p. per hour indicating that the engine is operating most economically 
throughout this range. 

The tests indicate a very good range of economical operation from 
f load to H load, and although the steam consumption is higher than the 
best recorded results for other engines of greater horsepower, yet the results 
obtained are very good considering the relatively small size of the engine. 

Appendix 

The engine under test was a 7f"Xl5" type "B" Buckeye engine which 
had been rebuilt from the old type of flat valve to a piston valve engine. The 
following information was supplied by the Buckeye Engine Company: 

Lap ji", Lead &", Compression 2\\ Exhaust laps, \ and A", Clearance 
5.6%, Cut-off 25%. Weight of reciprocating parts 150 pounds. 

The arrangement of the brake apparatus may be seen in Fig. 100, in which 
A is brake lever, B is calibrated brake load arc, C is brake pendulum, and D 
is brake wheel. 



192 STEAM ENGINES 

Cooling water for the brake enters through a hose not shown in the illus- 
tration. The direction of rotation of the brake wheel is indicated by the 
arrow near D. By means of the hand wheel E, the brake load is applied and 
regulated. The brake was carefully calibrated before beginning the test. 

Calibration of Constants 

47.173 X15 

H.E. piston displacement = — : — ■ = .41 cu. ft. 

144X12 

45 55 X15 

C.E. piston displacement = - — '- = .396 cu. ft. 

144X12 

.0252 

H.E. clearance = =6.15% 

.41 

C.E. clearance = : =6.765% 

.396 

15 X 47 173 

H.E. - i.h.p. Constant = '- — = .001787 

H 12X33000 

15 X45 55 

C.E. - i.h.p. Constant = : — = .001726 

P 12 X 33000 

B.H.P. Constant = .00060695 

33000 
Thermal Efficiency Constant = =42.42 

J 778 

Tables VI and VII contain information from the indicator diagrams, 
and Table VIII is a general summary of the observed and calculated results of 
the tests. 

Fig. 104 shows sample indicator diagrams taken during the test. 



INDEX 



INDEX 

PAGE 
A 

American locomobile 45 

B 

Buckeye engine determination of efficiency of under different loads 184 

appendix 191 

conclusions and comparisons 191 

method of conducting test ! 185 

observed data 185 

plan 184 

preliminary work 185 

purpose 184 

results 185 

Buckeye steam engine 36 

C 

Cameron belt-driven pump 68 

Compound pumping engine 7 

Condensers 123 

amount of cooling water per pound of steam 137 

cooling surface in surface condensers 138 

cost of cooling water determines condenser economy 134 

effect of condensation 123 

effect of condenser on efficiency 133 

feed water heaters 139 

relative merits of jet and surface condensers 132 

theory of condenser action 123 

types of 125 

Corliss steam engine 37 

advantages and disadvantages 39 

valve mechanism 37 

Crosshead and connecting rod 19 

Cylinder ratios : 29 

Cylinders 10 

D 

Deep- well or mine pump 69 

Duplex pump 70, 71 

E 

Engine mechanisms, analysis of 139 

crank effort 139 

diagrams 140 

variable thrust 140 



INDEX 

PAGE 

Engine mechanisms, analysis of (continued) 

flywheel 140 

governor 146 

Engine specifications 169 

contract 174 

drawing up specifications 169 

selecting an engine 169 

Engine tests 177 

A. S. M. E. Code 177 

importance of 177 

method of conducting 178 

F 

Farm or traction engine 50 

operation of plant 52 

road roller type 60 

semi-portable type 61 

Fly-ball governor 149 

Flywheel 140 

function 140 

size of wheel 141 

action of 142 

Foster superheater 117 

Frame 9 

G 

Governor 146 

fly-ball 149 

methods of action 146 

pendulum 147 

shaft 154 

J 

Jacketing 114 

jacket, function of 114 

saving due to jacketing 116 

L 

Locomotive engines 61 

boiler 61 

engine characteristics 64 

mechanical efficiency 63 

types of 65 

Losses, analysis of 108 

clearance Ill 

cooling by expansion 109 

exhaust waste 110 

friction Ill 

radiation 108 

steam condensation and re-evaporation 109 



INDEX 

PAGE 
M 

74 
Marine engines 

auxiliary apparatus 

condensers °" 

on 

pumps 

reversing mechanism ° 4 

definition of terms 

engine details 

bearings 

cranks 

crosshead guides 81 

cylinder 80 

marine details resemble stationary 81 

management of 

adjustments after starting 96 

before starting 93 

bilges " 

i no 
emergencies 1U 

hot bearings 97 

hot rods 98 

jackets " 

knocks 98 

linking up " 

lubrication 97 

marking off nuts 99 

refitting bearings *00 

starting engine ^4 

stopping vessel ^1 

methods of propulsion 75 

on 
propellers 

90 
screw 

propelling action of 91 

propulsion 

economical speed 89 

indicated thrust 89 

resistance factors for ship in motion 88 

ee 

starting , °° 

^re- 
types of ' ° 

beam ■ ' ° 

comparison of marine with stationary types 80 

cylinder 7 " 

inclined ' " 

vertical 7 " 

Mechanical and thermal efficiency 105 

analysis of losses *08 

losses in practical engine 1"7 

low thermal efficiency inherent 105 

Multiple expansion * 12 

exhaust waste utilized H4 



INDEX 

PAGE 

Multiple expansion (continued) 

less condensation 112 

methods of compounding 113 

N 

Newcomen steam engine 3 

Nordberg engine 42 

P 

Pendulum governor 147 

Piston rings 13 

Pistons 13 

Q 

Quadruple engines 28 

S 

Savery steam engine 1 

Separately-fired superheater 119 

Shaft governor 154 

Snap rings 13 

Stationary engines 31 

angle-compound type 39 

Buckeye vertical cross-compound type 36 

Corliss type 37 

Nordberg engine 42 

simple side-crank type 31 

simple vertical type 33 

advantages of vertical over horizontal type 34 

disadvantages of vertical type 35 

stationary types 49 

Uniflow steam engine 41 

Steam chest 19 

Steam engines 1-192 

annual operation expenses 176 

compound pumping engine 7 

cost of 174 

development 1 

early history 1 

engine mechanisms, analysis of 139 

engine specifications 169 

erection of 158 

foundations 158 

installations of attachments 160 

setting the engine 160 

marine engine 74 

mechanical and thermal efficiency 105 

Newcomen 3 



INDEX 

PAGE 

Steam engines (continued) 

operation of 161 

adjustment of connecting rod box 162 

adjusting eccentric strap 162 

care of bearing caps 161 

competent engineer a requisite 161 

governor 163 

lining up crosshead 162 

lubrication 163 

starting engine 168 

valve setting 163 

operation economies Ill 

condensers 123 

jacketing 114 

multiple expansion 112 

superheating 116 

parts of 7 

relative cost of operation items 175 

Savery 1 

tests 177 

types and construction 25 

Watt 5 

Stuffing box and packing 14 

Sub-base 8 

Superheaters, purposes of 120 

Superheating 116 

economic advantages 122 

Foster superheater 117 

general practice 116 

separately-fired superheater 119 

superheaters, purposes of 120 

T 

Tables 

Buckeye engine, performance of 190, 191 

cost of high speed, single cylinder engines 175 

cost of installation and operation for one year 176 

heights of governor for different speeds of engine 151 

increase in efficiency by use of condenser for various engines 134 

indicator diagram data for Buckeye engine test 188, 189 

price of single cylinder Corliss engines, set and erected 175 

Triple expansion engines 28 

Types and construction of steam engines 25 

classification 25 

compound engines 26 

farm or traction engine 50 

locomotive engine 61 

simple engines 26 

special engines 73 



INDEX 

PAGE 

Types and construction of steam engines (continued) 

stationary engines 31 

water pumps 67 

U 

Uniflow steam engine 41 

typical indicator cards 43 

V 

Valves 16 

W 

Water pumps 67 

crank or flywheel type 68 

direct-acting type 70 

Watt steam engine 5 




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